Sliding type tripod constant velocity joint

ABSTRACT

A sliding type tripod constant velocity joint includes an outer ring of a tubular form having three raceway grooves which are formed on an inner peripheral surface and which extend in a direction of a rotation axis of the outer ring, a tripod including a boss part connected to a shaft and three tripod shaft parts which are provided upright so as to extend outward in a radial direction of the boss part from an outer peripheral surface of the boss part and which are inserted into the raceway grooves, respectively, and an intermediate member which is provided on an outer periphery of a corresponding one of the tripod shaft parts so as to be oscillated relative to the corresponding one of the tripod shaft parts and which has power transmission surfaces on both side surfaces and opposing the side surfaces of a corresponding one of the raceway grooves.

The application is a Divisional application of co-pending applicationU.S. patent application No. 12/737,243, filed on Dec. 22, 2010, which isa National Stage of International Application No. PCT/JP2009/061411,filed on Jun. 23, 2009, which is based on and claims priority fromJapanese Patent Application Nos. 2008-164967 2008-164978, and2008-165016, filed on Jun. 24, 2008, the entire contents of which isincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a sliding type tripod constant velocityjoint.

BACKGROUND ART

As a usual sliding type tripod constant velocity joint, for instance, asliding type tripod constant velocity joint is known that is disclosedin JP-A-2000-256694 (Patent Document 1). In the sliding type tripodconstant velocity joint disclosed in Patent Document 1, a tripod shaftpart has a cylindrical form, and an inner peripheral surface of a rollerhas a cylindrical form. In this case, the roller is constantly locatedcoaxially with the tripod shaft part. Accordingly, when a joint angle isapplied, a direction in which the roller is apt to roll on a racewaygroove (a roller groove) does not correspond to a direction in which theraceway groove extends. Thus, a slide arises between the roller and theraceway groove. As result, an induced thrust force is generated in theaxial direction of the joint. The induced thrust force causes thevibration of a vehicle body or noise to be generated.

Thus, in order to reduce the induced thrust force, for instance, asliding type tripod constant velocity joint is known that is disclosedin JP-A-2006-162056 (Patent Document 2). In the sliding type tripodconstant velocity joint disclosed in Patent Document 2, an outerperipheral surface of a tripod shaft part has a spherical protrudingform and an inner peripheral surface of an inner roller forming a rollerunit abutting thereon has a cylindrical form. Thus, since the tripodshaft part can swing relative to the roller unit so that a direction inwhich an outer roller forming the roller unit is liable to roll on araceway groove may be made to constantly correspond to a direction inwhich the raceway groove extends, a slide can be avoided from arisingbetween the outer roller and the raceway groove. As a result, an inducedthrust force can be reduced.

Further, as other structures, structures are known that are disclosed inJP-A-63-163031 (Patent Document 3) and JP-B-2763624 (Patent Document 4).A sliding type tripod constant velocity joint disclosed in PatentDocument 3 includes a pair of intermediate members provided outside atripod shaft part and a needle arranged between the intermediate membersrespectively and a side surface of a raceway groove. Further, in asliding type tripod constant velocity joint disclosed in Patent Document4, a tubular and integral intermediate member is provided in an outerperiphery of a tripod shaft part, a needle can be circulated on an outerperipheral surface of the integral intermediate member and the needlerolls along the intermediate member and the side surface of a racewaygroove.

Further, as other structure, a structure is known that is disclosed inJP-A-2003-65350 (Patent Document 5). In a sliding type tripod constantvelocity joint disclosed in Patent Document 5, a rolling element is aspherical element. The rolling elements are mutually positioned relativeto an intermediate member and supported by a cage. When a power istransmitted in this structure, between the rolling element and theintermediate member, and between the rolling element and a racewaygroove, a large resistance is generated due to a slide as well as arolling resistance.

Thus, in order to reduce the resistance, for instance, structures areknown that are disclosed in JP-B-2763624 (Patent Document 4) andJP-B-3361096 (Patent Document 6). In sliding type tripod constantvelocity joints disclosed in Patent Documents 4 and 6, a rolling elementis a needle and supported by a cage on as to circulate on an outerperiphery of an intermediate member. Thus, a resistance between therolling element and the intermediate member, and between the rollingelement and a raceway groove due to a slide can be greatly reduced.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP-A-2000-256694

Patent Document 2: JP-A-2006-162056

Patent Document 3: JP-A-63-163031

Patent Document 4: JP-B-2763624

Patent Document 5: JP-A-2003-65350

Patent Document 6: JP-B-3361096

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

Here, in the constant velocity joint disclosed in Patent Document 2,when a joint angle is applied, the tripod shaft part slides in an axialdirection of the tripod shaft part relative to the roller unit.Accordingly, in the usual sliding type tripod constant velocity joint, aposition of the inner peripheral surface of the inner roller which abutson the tripod shaft part is changed. Thus, the roller unit operates soas to swing on a direction in which the raceway groove of an outer ringextends. Accordingly, a back surface side of a part of the roller unitthat transmits a power to the raceway groove of the outer ring abuts onthe raceway groove to generate a frictional force between the rollerunit and the raceway groove. As a result, there is a fear that theinduced thrust force may be increased. Further, a clearance between theraceway groove and the roller unit may be supposed to be enlarged toprevent the abutment of the back surface side, however, in such astructure, a rotation backlash of the roller unit may be probablyincreased.

Further, in the constant velocity joint disclosed in Patent Document 3,when a joint angle is small, the needle rolls on the raceway groove.However, since the number of the needles is limited to the finite numberin the direction in which the raceway groove extends, when the jointangle is large, the needle generates a slide relative to the racewaygroove and the intermediate member. The slide induces a thrust force tobe generated.

On the other hand, in the constant velocity joint disclosed in PatentDocument 4, since the needle circulates, the needle rolls relative tothe raceway groove and the intermediate member, so that a slide can beprevented from arising. However, since the intermediate member has anintegral structure, the same problem as that in the constant velocityjoint disclosed in Patent Document 2 arises. Namely, a state may begenerated that in a back surface side of a part which transmits a power,the intermediate member applies a force to an outer ring through theneedle. In such a way, the generation of the force in the back surfaceside induces to the thrust force to be generated.

Further, in the constant velocity joints disclosed in Patent Documents 4and 6, in order to transmit a power, the form of the rolling element orthe number of the rolling elements for transmitting the power at thesame time is suitably set. To sufficiently transmit the power, anextending direction (an entire length) of the raceway groove of a rollerunit needs to be increased to increase an abutting area of the rollerunit that contributes to the transmission of the power and a sidesurface of the raceway groove. When the entire length of the roller unitis increased, if a joint angle is applied, since a shaft may possiblyinterfere with the cage of the roller unit, a maximum joint angle isrestricted. When an outside diameter of an outer ring is enlarged, themaximum joint angle can be ensured, which is contrary to a request for acompact size.

Further, the cage for supporting the rolling element is requested toprevent the rolling element from falling under a state that the constantvelocity joint is attached and a lubricant is requested to be assuredlystuck to the rolling element to effectively circulate the rollingelement.

The present invention is made in view of such circumstances, and a firstobject of the present invention is to provide a sliding type tripodconstant velocity joint having a structure that a member abutting on araceway groove of an outer ring assuredly rolls on the raceway grooveand even when a tripod shaft part slides in the axial direction of thetripod shaft part relative to a roller unit, a back surface side of theroller unit can be prevented from applying a large force to the racewaygroove.

Further, a second object of the present invention is to provide asliding type tripod constant velocity joint that can avoid aninterference of a shaft and a roller unit when a joint angle isincreased without an enlargement. A third object of the presentinvention is to provide a sliding type tripod constant velocity jointthat can prevent a rolling element from falling under a state that theconstant velocity joint is rotated.

Means for Solving the Problem

A sliding type tripod constant velocity joint according to a firstaspect of the present invention includes: an outer ring of a tubularform having three raceway grooves which are formed on an innerperipheral surface and which extend in a direction of a rotation axis ofthe outer ring; a tripod including a boss part connected to a shaft andthree tripod shaft parts which are provided upright so as to extendoutward in a radial direction of the boss part from an outer peripheralsurface of the boss part and which are inserted into the racewaygrooves, respectively; a pair of intermediate members which are arrangedso as to sandwich a corresponding one of the tripod shaft parts fromboth sides of side surfaces of the raceway grooves and which areprovided so as to be oscillated relative to the corresponding one of thetripod shaft parts; a plurality of rolling elements provided between theside surfaces of a corresponding one of the raceway grooves and powertransmission surfaces of the pair of intermediate members opposing theside surfaces to the corresponding one of the raceway grooves so as toroll along the side surfaces of the corresponding one of the racewaygrooves; and a cage that supports the rolling elements such that therolling elements circulate on outer peripheries of the pair ofintermediate members.

According to the first aspect, since the rolling elements circulate onthe outer peripheries of the pair of intermediate members such that therolling elements roll along the raceway grooves, members that abut onthe raceway grooves of the outer ring assuredly roll relative to theraceway grooves. Accordingly, since the members that abut on the racewaygrooves of the outer ring can be prevented from sliding relative to theraceway grooves, an induced thrust force caused thereby can be preventedfrom being generated.

Further, in the roller unit of the constant velocity joint disclosed inthe Patent Documents 2 and 4, since during a power transmission, thetripod shaft parts slide so that a position of the inner peripheralsurface of the inner roller which abuts on the tripod shaft partschanges, the roller unit is oscillated together in the direction inwhich the raceway grooves of an outer ring extend to abut on the racewaygrooves in the back surface side of a part of the power transmission.Thus, the above-described problem arises.

As compared therewith, the present invention includes the one pair ofintermediate members arranged so as to sandwich the tripod shaft partsbetween them and provided so as to be oscillated relative to the tripodshaft parts. Namely, the one pair of intermediate members arerespectively independent. In such a way, even when a load position ischanged by the tripod shaft parts, which arises in a power transmissionside, an operation of the intermediate member of the power transmissionside does not give an influence to the operation of the intermediatemember of the back surface side. Accordingly, since the back surfaceside of the roller unit can be prevented from applying a large force tothe raceway grooves, the generation of the induced thrust force can begreatly reduced.

Here, the “roller unit” includes members that transmit a power from thetripod shaft parts to the raceway grooves. For instance, the roller unitin the tripod constant velocity joint disclosed in Patent Document 2includes an inner roller, an outer roller, a roller support member and asnap ring. The roller unit in the tripod constant velocity joint of thepresent invention includes the intermediate member, the rolling elementsand the cage.

According to a second aspect of the present invention, in the slidingtype tripod constant velocity joint of the first aspect, an outerperipheral surface of each of the tripod shaft parts has a sphericallyprotruding shape. Under a state where a rotation axis of the outer ringcoincides with a rotation axis of the shaft, a tripod PCR may bepreferably set to be larger than an outer ring PCR, where the tripod PCRis a distance between: a point on a tripod axis intersecting a planewhich passes through a center of width of the rolling element along thetripod axis and which is orthogonal to the tripod axis; and the rotationaxis of the outer ring, and where the tripod PCR is a distance between:a center of curvature of the outer peripheral surfaces of the tripodshaft parts; and the rotation axis of the shaft.

Here, if the outer ring PCR (pitch circle radius) is set to coincideswith the tripod PCR (pitch circle radius) under a position that therotation axis of the outer ring coincides with the rotation axis of theshaft, when the power is transmitted by applying a joint angle, acontact area of the tripod shaft parts and the roller unit slides in thedirection of width of the roller unit and a center of the sliding widthis located inside in the radial direction of the outer ring relative tothe roller unit. Therefore, for instance, when a spherical member isapplied to the rolling element, there is a fear that as the loadposition of the tripod shaft parts to the roller unit separates morefrom the center of width of the roller unit, a rotation backlash may bemore increased. Further, when a needle is applied to the rollingelement, there is a fear that a partial abrasion of the needle mayarise.

Thus, the tripod PCR is set to be larger than the outer ring PCR. Thus,when the power is transmitted by applying a prescribed joint angle, thecenter of the sliding width of the contact area of the tripod shaftparts and the roller unit can be located in the vicinity of a center inthe radial direction of the outer ring relative to the roller unit. As aresult, the rotation backlash can be reduced and the partial abrasion ofthe rolling element such as the needle can be prevented. However, ascompared with a case that the tripod PCR coincides with the outer ringPCR, when the tripod PCR is larger than the outer ring PCR, the loadposition of the tripod shaft parts to the roller unit is located outsidein the radial direction of the outer ring. Accordingly, a possibility isincreased that the roller unit comes into contact with the racewaygrooves of the outer ring in the back surface side of the powertransmission. However, since the one pair of intermediate members areindependent, the contact of the raceway grooves and the roller unit canbe avoided without increasing a clearance between the raceway groovesand the roller unit in the back surface side of the power transmission.

According to a third aspect of the present invention, in the slidingtype tripod constant velocity joint of the first aspect or the secondaspect, the pair of intermediate members have intermediate introducingsurfaces which are smooth with respect to the power transmissionsurfaces so as to smoothly contact and guide the circulating rollingelements to the power transmission surfaces.

Here, a member of a side of the one pair of intermediate members thattransmits the power is positioned relative to the tripod shaft parts andthe outer ring. On the other hand, since the cage is a member that doesnot contribute to the power transmission, a position of the cage is notstable. Accordingly, the rolling elements are not easily allowed toenter the power transmission surfaces of the intermediate members in aprescribed position from the cage whose position is not stabilized.Thus, the power transmission surfaces of the intermediate members andthe intermediate member introducing surfaces for allowing the rollingelements to enter the power transmission surfaces are formed with thesame member, so that the positions of the rolling elements entering thepower transmission surfaces can be stably adjusted.

According to a fourth aspect of the present invention, in the slidingtype tripod constant velocity joint of the third aspect, a circulatingpath as a track of the rolling elements circulated in the cage includes:a first circulating path where the rolling elements move on the powertransmission surfaces and which is defined along the power transmissionsurfaces; a second circulating path where the rolling elements move onthe intermediate member introducing surfaces and which is defined alongthe intermediate member introducing surfaces and is smoothly connectedto the first circulating path; and a third circulating path smoothlyconnected to side end parts of the second circulating path opposite tothe first circulating path.

Here, since the intermediate member introducing surface are not partsthat transmit the power between the raceway grooves and the intermediatemember introducing surfaces, a very large load is not applied to therolling elements moving on the intermediate member introducing surfaces.Accordingly, the rolling elements can be allowed to stably enter thesecond circulating path defined along the intermediate memberintroducing surfaces from the third circulating path. As a result, therolling elements can be smoothly moved from the third circulating pathto the second circulating path, and further, from the second circulatingpath to the first circulating path defined along the power transmissionsurfaces.

According to a fifth aspect of the present invention, in the slidingtype tripod constant velocity joint of any one of the first to fourthaspects, the cage may not be regulated in a power transmitting directionrelative to the one pair of intermediate members.

For instance, clearances are provided between all surfaces (includingthe power transmission surfaces and the intermediate member introducingsurfaces) of the one pair of intermediate members opposed to the sidesurfaces of the raceway grooves and the cage. Thus, the cage can preventthe rolling elements from acting so as to apply a force to the racewaygrooves of the outer ring in the back surface side of the powertransmission. Accordingly, the above-described effects can be assuredlyachieved.

According to a sixth aspect of the present invention, in the slidingtype tripod constant velocity joint of any one of the first to fifthaspects, the outer peripheral surfaces of the tripod shaft parts havethe spherically protruding shapes, and the inner surfaces of the onepair of intermediate members are fitted to the outer peripheral surfacesof the tripod shaft parts.

Since the one pair of intermediate members are spherically fitted to thetripod shaft parts on as to be oscillated, a load (face pressure) perunit area of the intermediate members can be reduced to improve thedurability of the intermediate members. Further, since the intermediatemembers follow the sliding tripod shaft parts, the positions thereof canbe fixed relative to the tripod shaft parts to stably transmit thepower. Further, in the present invention, since the one pair ofintermediate members are arranged so as to sandwich the tripod shaftparts between them, the inner surfaces thereof can be easily formed inentirely spherically recessed shapes. Accordingly, power transmissionareas of the tripod shaft parts and the one pair of intermediate memberscan be increased. Further, when the tripod shaft parts come into angularcontact with the intermediate members, two points of the angular contactare further spaced to be stabilized.

According to a seventh aspect of the present invention, in the slidingtype tripod constant velocity joint of any one of the first to fifthaspects, the rolling element is a cylindrical needle. Under a statewhere a rotation axis of the outer ring coincides with a rotation axisof the shaft, the cage may support the needle such that a cylindricalaxial direction of the needle is parallel to an axial direction of thetripod, and such that the pair of intermediate members may form thepower transmission surfaces which can slide in a radial direction of theouter ring relative to the needle.

Thus, since the needles abut on the side surfaces of the raceway groovesof the outer ring along the cylindrical axial direction to transmit thepower, in the roller unit, the rotation backlash is low as a whole sothat the power may be stably transmitted.

According to an eighth aspect of the present invention, in the slidingtype tripod constant velocity joint of any one the first to fifthaspects, the rolling element is a spherical or barrel shaped roller, andunder a state that a rotation axis of the outer ring coincides with arotation axis of the shaft, the pair of intermediate members may beprovided with the power transmission surfaces which can be oscillated ina radial direction of the outer ring relative to the rolling elements.

When the rolling element has the spherical shape, since the rollingelement is simple in its form and high in its rigidity and can be mostsmoothly circulated, the rolling element can stably transmit even alarge power. Further, when the rolling element is the barrel shapedroller, since a width in the direction orthogonal to the tripod axis canbe decreased more than that of the spherical rolling element, an entirewidth of the roller unit can be reduced. Further, when the intermediatemembers can be oscillated in the radial direction of the outer ringrelative to the rolling elements, the intermediate members can transmitthe power to the rolling elements depending on the position of thesliding tripod shaft parts. Here, the barrel shaped roller is therolling element that has a pillar shape and in which a section cut inthe direction orthogonal to the extending direction of the pillar iscircular and a part corresponding to an outer peripheral surface in asection cut in the extending direction of the pillar has a circular arcprotruding shape.

A sliding type tripod constant velocity joint according to a ninthaspect of the present invention includes: an outer ring of a tubularform having three raceway grooves which are formed on an innerperipheral surface and which extend in a direction of a rotation axis ofthe outer ring; a tripod including a boss part connected to a shaft andthree tripod shaft parts which are provided upright so as to extendoutward in a radial direction of the boss part from an outer peripheralsurface of the boss part and which are inserted into the racewaygrooves, respectively; an intermediate member which is provided on anouter periphery of a corresponding one of the tripod shaft parts so asto be oscillated relative to the corresponding one of the tripod shaftparts and which has power transmission surfaces on both side surfacesand opposing the side surfaces of a corresponding one of the racewaygrooves; a plurality of rolling elements provided between the sidesurfaces of the corresponding one of the raceway grooves and the powertransmission surfaces so as to roll along the side surfaces of thecorresponding one of the raceway grooves; and a cage that supports therolling elements such that the rolling elements circulate on an outerperiphery of the intermediate member, wherein the cage includes: a firstcirculating path which is located between one of the power transmissionsurfaces and one of the side surfaces of the corresponding one of theraceway grooves and which supports the rolling elements; a secondcirculating path which is located between the other of the powertransmission surfaces and the other of the side surfaces of thecorresponding one of the raceway grooves and which supports the rollingelements; a third circulating path which connects one ends of the firstand second circulating paths located in an opening side of the outerring and which is formed to be bent in at least in one direction of aradially outward direction of the outer ring and a direction toward thetripod shaft parts so as to have a protruding shape; and a fourthcirculating path which connects the other ends of the first and secondcirculating paths which are located in the interior side of the outerring.

According to the present invention, since the third circulating path isformed to be bent in a protruding shape at least in one direction of theradially outward direction of the outer ring and the direction towardthe tripod shaft parts, under a position where when the joint angle isapplied to transmit the power, the shaft comes closest to the cage, adistance of both the members is more increased than in a usual device.Accordingly, a maximum joint angle can be increased. Further, in such astructure, since a positional relation between the roller unit and thetripod shaft parts is not changed, the maximum joint angle can beincreased without enlarging the outside diameter of the outer ring.Therefore, an entire part of the constant velocity joint is not enlargedand the above-described effects can be achieved.

Here, especially, the case that the third circulating path is bent inthe protruding shape outward in the radial direction of the outer ringwill be described in detail. A circulating locus of the rolling elementswhen the roller unit is seen from the side surfaces of the racewaygrooves smoothly comes close linearly or in a circular arc shape tocirculating loci in the first and second circulating paths toward thebottom surfaces of the raceway grooves. Accordingly, since thecirculating locus is changed with a low resistance to an inertia forceacting on the circulating rolling elements, the smooth circulation ofthe rolling element is maintained and the maximum joint angle can beincreased.

Further, especially, the case that the third circulating path is bent inthe protruding shape in the direction toward the tripod shaft parts willbe described in detail. A circulating locus of the rolling elements whenthe roller unit is seen from the side surfaces of the raceway grooves isnot inclined to circulating loci in the first and second circulatingpaths. Namely, since the circulating loci is formed so as to be locatedin the same plane over an entire circumference, even in other rollingelements than a spherical member which hardly roll on an inclination,the maximum joint angle can be increased.

Further, the case that the third circulating path is bent in protrudingshapes in both the directions of the radially outward direction of theouter ring and the direction toward the tripod shaft parts. In order tobend the circulating path in the protruding shape outward in the radialdirection of the outer ring, a clearance from the roller unit to thebottom surfaces of the raceway grooves is necessary. However, even whenthe clearance is small, and accordingly, a sufficient bent part cannotbe formed, the circulating path may be bent in the protruding shape inthe direction toward to the tripod shaft parts. Thus, the contact of theshaft and the cage can be avoided and the maximum joint angle can beincreased.

According to a tenth aspect of the invention, in the sliding type tripodconstant velocity joint of the first aspect, a central part in acircumferential direction of the outer ring in the third circulatingpath is most bent in at least in one direction of the radially outwarddirection of the outer ring and the direction toward the tripod shaftparts so as to have the protruding shape.

Thus, when the third circulating path is most bent in the protrudingshape at least in one direction of the radially outward direction of theouter ring and the direction toward the tripod shaft parts, thecirculating locus of the rolling elements in the third circulating pathis formed so as to be symmetrical with respect to the tripod axis whenthe third circulating path is seen from the direction of the rotationaxis of the outer ring. Thus, the circulating path can be formed so thateven when a direction in which the rolling elements of the roller unitreciprocating on the raceway grooves are circulated is reversed when thepower is transmitted, the rolling elements are supported by the cagesimilarly to a state before the reversing operation, a stablecirculation is held and the maximum joint angle is increased

According to an eleventh aspect of the present invention, in the slidingtype tripod constant velocity joint of the tenth aspect, the first,second, third and fourth circulating paths have opening parts over anentire length in an outer peripheral side of the cage, and widths of theopening parts of the third and fourth circulating paths may be narrowerthan widths of the opening parts of the first and second circulatingpaths.

Here, the opening parts of the first and second circulating paths arepreferably formed to be large so that the cage which supports therolling elements to be circulated supports the rolling elements in thepower transmission part and does not block the power transmission of therolling elements and the side surfaces of the raceway grooves. On theother hand, in order to prevent thee rolling elements from falling undera state the constant velocity joint is attached, the width of theopening parts of the third and fourth circulating paths is preferablyset to be narrower than the width of the opening parts of the first andssecond circulating paths. On the rolling elements circulating on thethird and fourth circulating paths, a large inertia force is exerted inthe direction of the rotation axis of the outer ring and other memberfor regulating the inertia force is not provided. Accordingly, when thewidth of the opening parts of the third and fourth circulating paths isenlarged, there is a fear that when the inertia force acting on therolling elements is large, the rolling elements may possibly fall fromthe cage. Thus, the width of the opening parts in the third and fourthcirculating paths is suitably set to be narrower than the width of theopening parts of the first and second circulating paths. Thus, thecirculation of the rolling elements is not blocked and the rollingelements can be prevented from falling from the cage.

According to a twelfth aspect of the present invention, in the slidingtype tripod constant velocity joint of any one of the ninth to eleventhaspects, the third and fourth circulating paths are formed to besymmetrical with respect to the corresponding one of the tripod shaftparts.

Thus, since the form obtained by bending the third and fourthcirculating paths in the protruding shapes or the form obtained bynarrowing the width of the opening parts is a symmetrical form withrespect to the tripod shaft parts, there is no difference as membersbetween the first and second circulating paths, and third and fourthcirculating paths. Accordingly, during the attachment of the constantvelocity joint, an erroneous attachment such as an attachment oppositeto an initial design can be prevented.

A sliding type tripod constant velocity joint according to a thirteenthaspect of the present invention includes: an outer ring of a tubularform having three raceway grooves which are formed on an innerperipheral surface and which extend in a direction of a rotation axis ofthe outer ring; a tripod including a boss part connected to a shaft andthree tripod shaft parts which are provided upright so as to extendoutward in a radial direction of the boss part from an outer peripheralsurface of the boss part and which are inserted into the racewaygrooves, respectively; an intermediate member which is provided on anouter periphery of a corresponding one of the tripod shaft parts so asto be oscillated relative to the corresponding one of the tripod shaftparts and which has power transmission surfaces on both side surfacesand opposing the side surfaces of a corresponding one of the racewaygrooves; a plurality of rolling elements provided between the sidesurfaces of the corresponding one of the raceway grooves and the powertransmission surfaces so as to roll along the side surfaces of thecorresponding one of the raceway grooves; and a cage that supports therolling elements such that the rolling elements circulate on an outerperiphery of the intermediate member, wherein the cage includes: a firstcirculating path which is located between one of the power transmissionsurfaces and one of the side surfaces of the corresponding one of theraceway grooves and which supports the rolling elements; a secondcirculating path which is located between the other of the powertransmission surfaces and the other of the side surfaces of thecorresponding one of the raceway grooves and which supports the rollingelements; a third circulating path which connects one ends of the firstand second circulating paths located in an opening side of the outerring; and a fourth circulating path which connects the other ends of thefirst and second circulating paths located in an interior side of theouter ring, wherein the first, second, third and fourth circulatingpaths have opening parts over an entire length in an outer peripheralside of the cage, and wherein widths of the opening parts of the thirdand fourth circulating paths are narrower than widths of the openingparts of the first and second circulating paths.

According to the present invention, the width of the opening parts inthe third and fourth circulating paths is suitably set to be narrowerthan the width of the opening parts of the first and second circulatingpaths. Thus, the circulation of the rolling elements is not blocked andthe rolling elements can be prevented from falling from the cage.

According to a fourteenth aspect of the present invention, in thesliding type tripod constant velocity joint of the thirteenth aspect,the third circulating path and the fourth circulating path are formed tobe symmetrical with respect to the corresponding one of the tripod shaftparts.

Thus, since the form obtained by narrowing the width of the openingparts of the third and fourth circulating paths is a symmetrical formwith respect to the tripod shaft parts, there is no difference asmembers between the first and second circulating paths, and third andfourth circulating paths. Accordingly, during the attachment of theconstant velocity joint, an erroneous attachment such as an attachmentopposite to an initial design can be eliminated.

A sliding type tripod constant velocity joint according to a fifteenthaspect of the present invention includes: an outer ring of a tubularform having three raceway grooves which are formed on an innerperipheral surface and which extend in a direction of a rotation axis ofthe outer ring; a tripod including a boss part connected to a shaft andthree tripod shaft parts which are provided upright so as to extendoutward in a radial direction of the boss part from an outer peripheralsurface of the boss part and which are inserted into the racewaygrooves, respective; an intermediate member which is provided on anouter periphery of a corresponding one of the tripod shaft parts so asto be oscillated relative to the corresponding one of the tripod shaftparts and which has power transmission surfaces on outer surfaces andopposing the side surfaces of a corresponding one of the racewaygrooves; a plurality of rolling elements provided between the sidesurfaces of the corresponding one of the raceway grooves and the powertransmission surfaces so as to roll along the side surfaces of thecorresponding one of the raceway grooves; and a cage that supports therolling elements such that the rolling elements circulate on an outerperiphery of the intermediate member, wherein under a state where arotation axis of the outer ring coincides with a rotation axis of theshaft, a central axis of the corresponding one of the tripod shaft partsis closer to an opening side of the outer ring than to a central part ofa width of the power transmission surfaces in the direction of therotation axis of the outer ring.

According to the present invention, since the central axis of the tripodshaft parts is set nearer to the opening side of the outer ring than tothe central part of the width of the power transmission surfaces in theintermediate member in the direction of the rotation axis of the outerring, it may be said that the central axis of the tripod shaft parts isset nearer to the opening side of the outer ring than to the centralpart of an entire length in the roller unit. Thus, under a positionwhere when the joint angle is applied to transmit the power, the cagelocated outside the roller unit comes closest to the shaft, a distancebetween both the members is increased more than that in a usual device.Accordingly, the maximum joint angle can be increased. Further, in sucha structure, since the position of the roller unit is not changedoutward in the radial direction of the outer ring, the maximum jointangle can be increased without enlarging the diameter of the outer ring.Accordingly, an entire part of the constant velocity joint is notenlarged and the above-described effects can be achieved.

Here, the “roller unit” includes members that transmit the power fromthe tripod shaft parts to the raceway grooves. For instance, a rollerunit in a double roller type tripod constant velocity joint includes aninner roller, an outer roller, a roller support member and a snap ring.The roller unit in the tripod constant velocity joint of the presentinvention includes the intermediate member, the rolling elements and thecage.

According to a sixteenth aspect of the present invention, in the slidingtype tripod constant velocity joint of the fifteenth aspect, under thestate where the rotation axis of the outer ring coincides with therotation axis of the shaft, the central axis of the corresponding one ofthe tripod shaft parts may be closer to the opening side of the outerring than to a central part of a width of the cage in the direction ofthe rotation axis of the outer ring.

Thus, under a position where when the joint angle is applied to transmitthe power, the cage located outside the roller unit comes closest to theshaft, a distance both the members is increased more than that in ausual device. Accordingly, the maximum joint angle can be more assuredlyincreased.

According to a seventeenth aspect of the present invention, in thesliding type tripod constant velocity joint of the fifteenth orsixteenth aspect under the state where the rotation axis of the outerring coincides with the rotation axis of the shaft, the central axis ofthe corresponding one of the tripod shaft parts may be closer to theopening side of the outer ring than to a central part of a width of thepower transmission surfaces of the intermediate member in the directionof the rotation axis of the outer ring.

Thus, since the central axis of the tripod shaft parts is set nearer tothe opening side of the outer ring relative to the central part of anentire part of the intermediate member, the maximum joint angle can bemore assuredly increased.

According to an eighteenth aspect of the present invention, in thesliding type tripod constant velocity joint of any one of the fifteenthto the seventeenth aspects, the cage is formed to be symmetrical withrespect to the direction of the rotation axis of the outer ring. Thus,when the cage is seen with the direction of the rotation axis of theouter ring set as a transverse direction, the cage is symmetricallyformed from a central part. Thus, even when the maximum joint angle isto be increased by changing the design of the intermediate member in theabove-described means, since the cage is symmetrically formed, duringthe attachment of the roller unit, the erroneous attachment such as theattachment opposite to an initial design can be prevented.

A sliding type tripod constant velocity joint according to a nineteenthaspect of the present invention includes: an outer ring of a tubularform having three raceway grooves which are formed on an innerperipheral surface and which extend in a direction of a rotation axis ofthe outer ring; a tripod including a boss part connected to a shaft andthree tripod shaft parts which are provided upright so as to extendoutward in a radial direction of the boss part from an outer peripheralsurface of the boss part and which are inserted into the racewaygrooves, respectively; an intermediate member which is provided on anouter periphery of a corresponding one of the tripod shaft parts so asto be oscillated relative to the corresponding one of the tripod shaftparts and which has power transmission surfaces on both side surfacesand opposing the side surfaces of a corresponding one of the racewaygrooves; a plurality of rolling elements provided between the sidesurfaces of the corresponding one of the raceway grooves and the powertransmission surfaces so as to roll along the side surfaces of thecorresponding one of the raceway grooves; and a cage that supports therolling elements such that the rolling elements circulate on an outerperiphery of the intermediate member, wherein under a state where arotation axis of the outer ring coincides with a rotation axis of theshaft, a central axis of the corresponding one of the tripod shaft partsis closer to an opening side of the outer ring than to a central part ofa width of the cage in the direction of the rotation axis of the outerring.

According to the present invention, since the central axis of the tripodshaft parts is set nearer to the opening side of the outer ring than tothe central part of the width of the cage in the direction of therotation axis of the outer ring, it may be said that the central axis ofthe tripod shaft parts is set nearer to the opening side of the outerring than to the central part of an entire length in the roller unit.Thus, under a position where when the joint angle is applied to transmitthe power, the cage located outside the roller unit comes closest to theshaft, a distance between both the members is increased more than thatin a usual device. Accordingly, the maximum joint angle can beincreased. Further, in such a structure, since the position of theroller unit is not changed outward in the radial direction of the outerring, the maximum joint angle can be increased without enlarging thediameter of the outer ring. Accordingly, an entire part of the constantvelocity joint is not enlarged and the above-described effects can beachieved.

A sliding type tripod constant velocity joint according to a twentiethaspect of the present invention includes: an outer ring of a tubularform having three raceway grooves which are formed on an innerperipheral surface and which extend in a direction of a rotation axis ofthe outer ring; a tripod including a boss part connected to a shaft andthree tripod shaft parts which are provided upright so as to extendoutward in a radial direction of the boss part from an outer peripheralsurface of the boss part and which are inserted into the racewaygrooves, respectively; an intermediate member which is provided on anouter periphery of a corresponding one of the tripod shaft parts so asto be oscillated relative to the corresponding one of the tripod shaftparts and which has power transmission surfaces on both side surfacesand opposing the side surfaces of a corresponding one of the racewaygrooves; a plurality of rolling elements provided between the sidesurfaces of the corresponding one of the raceway grooves and the powertransmission surfaces so as to roll along the side surfaces of thecorresponding one of the raceway grooves; and a cage that supports therolling elements such that the rolling elements circulate on an outerperiphery of the intermediate member, wherein under a state where arotation axis of the outer ring coincides with a rotation axis of theshaft, a central axis of the corresponding one of the tripod shaft partsis closer to an opening side of the outer ring than to a central part ofa width of the intermediate member in the direction of the rotation axisof the outer ring.

According to the present invention, since the central axis of the tripodshaft parts is set nearer to the opening side of the outer ring than tothe central part of the width of the intermediate member in thedirection of the rotation axis of the outer ring, it may be said thatthe central axis of the tripod shaft parts is set nearer to the openingside of the outer ring than to the central part of an entire length inthe roller unit. Thus, under a position where when the joint angle isapplied to transmit the power, the cage located outside the roller unitcomes closest to the shaft, a distance between both the members isincreased more than that in a usual device. Accordingly, the maximumjoint angle can be increased. Further, in such a structure, since theposition of the roller unit is not changed outward in the radialdirection of the outer ring, the maximum joint angle can be increasedwithout enlarging the diameter of the outer ring. Accordingly, an entirepart of the constant velocity joint is not enlarged and theabove-described effects can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first exemplary embodiment: a diagram seen from anopening side of an outer ring 10 in an attached state of a part of aconstant velocity joint 1.

FIG. 2 is a radially sectional view of a part of the constant velocityjoint 1.

FIG. 3 is a perspective view of a roller unit 30.

FIG. 4( a) is a plan view of the roller unit 30, FIG. 4( b) is asectional view of the roller unit 30 taken along a line A-A (a sectionalview of a minor axis side) and FIG. 4( c) is a partly sectional view ofthe roller unit 30 taken along a line B-B (a diagram including a partialsection of a major axis side).

FIG. 5 is one perspective view of a pair of intermediate members 40.

FIG. 6( a) is a front view of the intermediate member 40, FIG. 6( b) isa partly sectional view of the intermediate member 40 taken along a lineE-E, FIG. 6( c) is a diagram seen from a direction F of the intermediatemember 40, FIG. 6( d) is a sectional view of the intermediate member 40taken along a line G-G and FIG. 6( e) is a sectional view of theintermediate member 40 taken along a line H-H.

FIG. 7 is a perspective view of a cage 60.

FIG. 8( a) is a plan view of the cage 60, FIG. 8( b) is a sectional viewof the cage 60 taken along a line C-C (a sectional view of a minor axisside) and FIG. 8( c) is a sectional view of the cage 60 taken along aline D-D (a diagram including a partial section of a major axis side).

FIG. 9 shows a second exemplary embodiment: a radially sectional view ofa part of a constant velocity joint 101.

FIG. 10 is a perspective view of a roller unit 130.

FIG. 11 is a perspective view of a cage 160.

FIG. 12( a) is a plan view of the cage 160. FIG. 12( b) is a view of thecage 160 seen from a direction J and FIG. 12( c) is a sectional view ofthe cage 160 taken along a line K-K (a diagram including a partialsection of a major axis side).

FIG. 13 is one perspective view of a pair of intermediate members 140.

FIG. 14( a) is a front view of the intermediate member 140. FIG. 14( b)is a partly sectional view of the intermediate member 140 taken along aline L-L, FIG. 14( c) is a diagram seen from a direction M of theintermediate member 140 and FIG. 14( d) is a sectional view of theintermediate member 140 taken along a line N-N.

FIG. 15 shows a third exemplary embodiment: a radially sectional view ofa part of a constant velocity joint 201.

FIG. 16 shows a fourth exemplary embodiment: a radially sectional viewof a part of a constant velocity joint 301.

FIG. 17 is a diagram seen from an opening side of an outer ring 10 inthe constant velocity joint 301 to which a prescribed joint angle isapplied.

FIG. 18 is a diagram seen from an opening side of the outer ring 10 inthe constant velocity joint 301 to which a prescribed joint angle isapplied.

FIG. 19 is a graph showing a joint angle and a maximum and minimumcontact point moving amount for each offset amount.

FIG. 20 shows a fifth exemplary embodiment: a radially sectional view ofa part of a constant velocity joint 401.

FIG. 21 is a graph showing a joint angle and a rotation backlash foreach offset amount.

FIG. 22 is a perspective view of a roller unit 530.

FIG. 23( a) is a plan view of the roller unit 530, FIG. 23( b) is asectional view of the roller unit 530 taken along a line A-A (asectional view of a minor axis side) and FIG. 23( c) is a partlysectional view of the roller unit 530 taken along a line B-B (a diagramincluding a partial section of a major axis side).

FIG. 24 is a perspective view of a cage 560.

FIG. 25( a) is a plan view of the cage 560. FIG. 25( b) is a sectionalview of the cage 560 taken along a line D-D (a sectional view of a minoraxis side) and FIG. 25( c) is a sectional view of the cage 560 takenalong a line E-E (a diagram including a partial section of a major axisside).

FIG. 26 is a sectional view seen from a direction orthogonal to arotation axis of an outer ring 10 in an attached state of a part of aconstant velocity joint 501.

FIG. 27 is a top view of a cage 660.

FIG. 28 shows a seventh exemplary embodiment: a radially sectional viewof a part of a constant velocity joint 701.

FIG. 29 is a perspective view in an attached state of a part of theconstant velocity joint 701.

FIG. 30 is a perspective view of a cage 760.

FIG. 31( a) is a plan view of the cage 760. FIG. 31( b) is a view of thecage 760 seen from a direction F (a sectional view of a minor axis side)and FIG. 31( c) is a sectional view of the cage 760 taken along a lineF-F (a diagram including a partial section of a major axis side).

FIG. 32 is a perspective view in an attached state of a part of aconstant velocity joint 801 of an eighth exemplary embodiment.

FIG. 33 is a perspective view of a cage 860.

FIG. 34 is a perspective view of a roller unit 930.

FIG. 35( a) is a plan view of the roller unit 930, FIG. 35( b) is asectional view of the roller unit 930 taken along a line A-A (asectional view of a minor axis side) and FIG. 35( c) is a partlysectional view of the roller unit 930 taken along a line B-B (a diagramincluding a partial section of a major axis side).

FIG. 36 is one perspective view of a pair of intermediate members 940.

FIG. 37( a) is a front view of the intermediate member 940. FIG. 37( b)is a side view of the intermediate member 940 and FIG. 37( c) is a viewof the intermediate member 940 seen from a direction C.

FIG. 38 is a perspective view of a cage 960.

FIG. 39( a) is a plan view of the cage 960, FIG. 39( b) is a sectionalview of the cage 960 taken along a line D-D (a sectional view of a minoraxis side) and FIG. 39( c) is a sectional view of the cage 960 takenalong a line E-E (a diagram including a partial section of a major axisside).

FIG. 40 is a sectional view seen from a direction orthogonal to arotation axis of an outer ring 10 in an attached state of a part of aconstant velocity joint 901.

FIG. 41 is a radially sectional view of a part of a constant velocityjoint 1001 of a tenth exemplary embodiment.

FIG. 42 is a diagram seen from an axial direction of a tripod of theconstant velocity joint 1001 excluding an outer ring.

FIG. 43 is a diagram seen from a direction orthogonal to a rotation axisof the outer ring of the constant velocity joint 1001 excluding theouter ring.

FIG. 44 is a perspective view in an attached state of a part of aconstant velocity joint 1101 of an eleventh exemplary embodiment.

MODE FOR CARRYING OUT THE INVENTION

Now, exemplary embodiments that embody a sliding type tripod constantvelocity joint (refer it simply to as a “constant velocity joint”,hereinafter) of the present invention will be described below byreferring to the drawings. Here, as the constant velocity joint of thepresent exemplary embodiment, a case that the constant velocity joint isused for connecting a power transmission shaft of a vehicle will bedescribed as an example. For instance, the case shows that the constantvelocity joint is used in a connecting part of a shaft part connected toa differential gear and an intermediate shaft of a drive shaft.

First Exemplary Embodiment

A constant velocity joint 1 of a first exemplary embodiment will bedescribed by referring to FIGS. 1 to 8. FIG. 1 is a diagram seen from anopening side of an outer ring 10 in an attached state of a part of theconstant velocity joint 1. FIG. 2 is a radially sectional view of a partof the constant velocity joint 1. FIG. 3 is a perspective view of aroller unit 30. FIG. 4( a) is a plan view of the roller unit 30, FIG. 4(b) is a sectional view of the roller unit 30 taken along a line A-A (asectional view of a short diameter side) and FIG. 4( c) is a partlysectional view of the roller unit 30 taken along a line B-B (a diagramincluding a partial section of a long diameter side). FIG. 5 is oneperspective view of a pair of intermediate members 40. FIG. 6( a) is afront view of the intermediate member 40, FIG. 6( b) is a partlysectional view of the intermediate member 40 taken along a line E-E,FIG. 6( c) is a diagram seen from a direction F of the intermediatemember 40, FIG. 6( d) is a sectional view of the intermediate member 40taken along a line G-G and FIG. 6( e) is a sectional view of theintermediate member 40 taken along a line H-H. FIG. 7 is a perspectiveview of a cage 60. FIG. 8( a) is a plan view of the cage 60, FIG. 8( b)is a sectional view of the cage 60 taken along a line C-C (a sectionalview of a short diameter side) and FIG. 8( c) is a sectional view of thecage 60 taken along a line D-D (a diagram including a partial section ofa long diameter side).

As shown in FIGS. 1 and 2, the constant velocity joint 1 includes anouter ring 10, a tripod 20 and a roller unit 30.

The outer ring 10 is formed in a tubular shape (for instance, a tubularshape having a bottom) and has one end side connected to a differentialgear (not shown in the drawing). Then, in an inner peripheral surface ofthe tubular part of the outer ring 10, three raceway grooves 11 thatextend in the axial direction (a forward and backward direction inFIG. 1) of the outer ring are formed at equal intervals in thecircumferential direction of an outer ring shaft. A sectional formorthogonal to an extending direction of a groove in each raceway groove11 has a U shape. Namely, each raceway groove 11 includes a groovebottom surface substantially formed in a plane and side surfaces formedin planes orthogonal to the groove bottom surface and opposed inparallel with each other.

Further, in both opening edges of the raceway groove 11, engagingprotrusions 12 are formed which narrow opening width of the racewaygroove 11. The engaging protrusions 12 serve to regulate a position of acage 60 forming a below-described roller unit 30. Namely, the cage 60 isconstantly located in the raceway groove 11 by the engaging protrusions12.

The tripod 20 is arranged inside the tubular part of the outer ring 10.The tripod 20 includes a boss part 21 and three tripod shaft parts 22.The boss part 21 has a tubular form and is provided with an innerperipheral spline 21 a in an inner peripheral side. The inner peripheralspline 21 a is fitted and connected to an outer peripheral spline of anintermediate shaft (not shown in the drawings). Further, an outerperipheral surface of the boss part 21 is formed substantially in aspherically protruding shape.

The tripod shaft parts 22 are respectively provided upright so as toextend radially outward the boss part 21 from the outer peripheralsurface of the boss part 21. These tripod shaft parts 22 are formed atequal intervals (at intervals of 120 deg) in the circumferentialdirection of the boss part 21. At least end parts of the tripod shaftparts 22 are respectively inserted into the raceway moves 11 of theouter ring 10. The outer peripheral surfaces of the tripod shaft parts22 are respectively formed in spherically protruding shapes.

The roller unit 30 is formed in an annular shape as an entire shape asshown in FIGS. 3 and 4 and arranged in an outer peripheral side of thetripod shaft parts 22. Further, the roller unit 30 is fitted to theraceway grooves 11 so as to be movable in the direction in which theraceway grooves 11 extend. The roller unit 30 includes an intermediatemember 40, a plurality of rolling elements 50 and a cage 60.

An outer form of the intermediate member 40 is configured substantiallyin a rectangular shape as an entire form. Further, when the intermediatemember 40 is observed as a whole, a part corresponding to a circularhole is formed in a center of the intermediate member 40. Theintermediate member 40 includes a pair of members 40 a and 40 b. The onepair of intermediate members 40 a and 40 b are formed by separatemembers so as to have symmetrical forms relative to a plane passingthorough a central axis (it is also referred to as a “tripod axis”) ofthe tripod shaft part 22 and a rotation axis of an intermediate shaftand respectively independent. The one pair of intermediate members 40 aand 40 b are arranged, as shown in FIG. 2, so as to sandwich the tripodshaft part 22 from both sides of side surfaces of the raceway grooves11. Namely, both the intermediate members 40 a and 40 b are arranged soas to sandwich the tripod shaft part 22 from both sides in a powertransmitting direction (a direction on the rotation axis of the outerring or on the rotation axis of the intermediate shaft). The one pair ofintermediate members 40 a and 40 b are provided so as to oscillate inthe direction of the rotation axis of the outer ring 10 relative to thetripod shaft part 22 and oscillate in the circumferential direction ofthe outer ring 10.

A detailed form of each of the intermediate members 40 a and 40 b willbe described by referring to FIG. 5 and FIGS. 6( a) to 6(d). The surfaceof each of the intermediate members 40 a and 40 b includes a tripodcontact surface 41, a power transmission surface 42, intermediate memberintroducing surfaces 43 and axial end faces 44 and 45. Here, when theone pair of intermediate members 40 a and 40 b are seen as one body, thetripod contact surfaces 41 form an inner surface and the powertransmission surfaces 42, the intermediate member introducing surfaces43 and the axial end faces 44 and 45 form an outer surface.

The tripod contact surface 41 is formed in a partly spherically recessedshape to come into contact with the tripod shaft part 22 an as tooscillate in the axial direction of the outer ring 10 and in thecircumferential direction of the outer ring 10. A center of a sphericalsurface of the tripod contact surface 41 is located on a straight linepassing thorough a center of a transverse width (the thickness of theintermediate member 40) of the tripod contact surface 41 shown in FIG.6( a) and a center of a vertical width (a width of the intermediatemember 40 in the axial direction of the outer ring 10) shown in FIG. 6(b).

The power transmission surface 42 and the intermediate memberintroducing surfaces 43 are provided in a back surface side of thetripod contact surface 41, that is, in the right side in FIG. 6( b). Thepower transmission surface 42 is formed in a planar and rectangularshape. The intermediate members 40 a and 40 b are respectively arrangedso that the power transmission surface 42 is parallel to the sidesurfaces of the raceway groove 11. Namely, under a position that therotation axis of the outer ring 10 coincides with the rotation axis ofthe intermediate shaft (a joint angle of 0 deg), the power transmissionsurface 42 is parallel to the plane passing thorough the central axis ofthe tripod shaft part 22 and the rotation axis of the intermediateshaft. Further, the power transmission surface 42 is located at acentral part in the vertical direction shown in FIG. 6( b) and has awidth about ⅔ times as long as the vertical width shown in FIG. 6( b).Namely, in the back surface side of the deepest part of the tripodcontact surface 41, the power transmission surface 42 is located. Thepower transmission surface 42 includes a range where the powertransmission surface may come into contact with the plurality of rollingelements 50.

The intermediate member introducing surfaces 43 are formed at both sidesadjacent to the power transmission surface 42. The intermediate memberintroducing surfaces 43 are formed with slightly bent curved surfacesand smoothly formed relative to the power transmission surface 42(continuously without stepped parts). The intermediate memberintroducing surfaces 43 protrude outward and are bent toward sides whichdo not protrude from the plane of the power transmission surface 42.Namely, the intermediate member introducing surfaces 43 are bent moretoward sides separating from the side surfaces of the raceway groove 11,as the intermediate member introducing surfaces come nearer to the axialend faces 44 and 45 sides from the power transmission surface 42 side.Further, the intermediate member introducing surfaces 43 are formedsubstantially in trapezoidal shapes in such a way that as theintermediate member introducing surfaces 43 come nearer to the axial endfaces 44 and 45 sides from the power transmission surface 42 side, thetransverse width of FIG. 6( a) is the more reduced. The intermediatemember introducing surfaces 43 come into contact with and guide therolling elements 50 which are circulated on the outer periphery of theintermediate member 40 no as to smoothly enter the power transmissionsurface 42 and smoothly discharge the rolling elements 50 from the powertransmission surface 42.

The axial end faces 44 and 45 are parts located at both ends in upperand lower parts in FIG. 6( b). Both the axial end faces 44 and 45 areformed with planes orthogonal to the power transmission surface 42.Namely, the axial end faces 44 and 45 are formed with planes orthogonalto the side surfaces of the raceway groove 11. Here, horizontallysectional forms of FIGS. 6( a) and 6(b) in the intermediate members 40respectively show regular triangular shapes as shown in FIGS. 6( c) and6(e). The axial end faces 44 and 45 also have regular triangular shapesas shown in FIG. 6( d).

The rolling element 50 is a needle as shown in FIGS. 2 and 4. Therolling element 50 includes a cylindrical part 51 and small diametershaft parts 52 having a circular section cut in the direction (atransverse direction in FIG. 2) orthogonal to an extending direction ofthe pillar and provided at both ends in the extending direction of thepillar. As shown in FIG. 4( b), the small diameter shaft part 52 mayhave a form whose diameter is smaller as the small diameter shaft part52 comes nearer to the end part or a stepped form (not shown in thedrawings). The plurality of rolling elements 50 are provided so as tocirculate on an outer periphery when the one pair of intermediatemembers 40 a and 40 b are seen as one body. A part of the plurality ofrolling elements 50 is provided between the side surface of the racewaygroove 11 and the power transmission surfaces 42 of the one pair ofintermediate members 40 a and 40 b so as to roll along the side surfaceof the raceway groove 11 and the power transmission surfaces 42. Thatis, a power is transmitted between the power transmission surfaces 42and the side surface of the raceway groove 11 through the rollingelements 50.

As shown in FIGS. 7 and 8( a), the cage 60 has an annular shape as anentire form. The cage 60 includes a pair of circulating path formingmembers 61 and 62 that form a circulating path of the rolling elements50 and a pair of connecting parts 63 and 64. The one pair of circulatingpath forming members 61 and 62 are located in peripheral edges of thecage 60 and have elliptic forms. The one pair of circulating pathforming members 61 and 62 have such forms as to surround the one pair ofintermediate members 40 a and 40 b.

Specifically, the circulating path forming member 61 includes opposedstraight line parts 61 a and 61 b and semi-circular arc shaped bentparts 61 c and 61 d for connecting the straight line parts 61 a and 61b. Further, another circulating path forming member 62 includes straightline parts and bent parts similarly to the above -described circulatingpath forming member 61.

Further, one pair of circulating path forming members 61 and 62 arerespectively configured in U shaped sectional forms into which the smalldiameter shaft parts 52 of the rolling element 50 can be inserted andwith which the cylindrical part 51 is engaged. Namely, a width (adistance between an inner peripheral edge and an outer peripheral edge)of the one pair of circulating path forming members 61 and 62 is formedto be smaller than a maximum diameter of the cylindrical part 51 of therolling element 50. Under a state that the U shaped opening sides of thecirculating path forming members 61 and 62 are spaced by a distancelonger than the axial length of the cylindrical part 51 of the rollingelement 50, the U shaped opening sides are provided so as to be opposedto each other. A maximum width between the one pair of circulating pathforming members 61 and 62 in an opposing direction is set to be slightlysmaller than the width of the side surface of the raceway groove 11.Namely, the cage 60 is provided on that an inclination thereof isregulated relative to the raceway groove 11 by the groove bottom surfaceand the engaging protrusions 12 of the raceway groove 11 and the cagemay be inserted into the raceway groove 11.

The one pair of connecting parts 63 and 64 respectively connect togethercentral parts (upper and lower end parts in FIG. 8( a))in thecircumferential direction of the bent parts 61 c and 61 d of the onepair of circulating path forming members 61 and 62. Namely, as shown inFIG. 8( c), a part between the one pair of circulating path formingmembers 61 and 62 is opened in a part excluding the connecting parts 63and 64.

The connecting parts 63 and 64 are configured in U shaped forms openedoutward the cage 60. Bottom surfaces opposite to opening sides of the Ushaped forms of the connecting parts 63 and 64 (an inner side of thecage 60) are formed to be flat. The bottom surfaces opposite to theopening sides of the U shaped forms of the one pair of connecting parts63 and 64 are provided so as to be parallel and opposed to each other. Aclearance between the bottom surfaces opposite to the opening sides ofthe U shaped forms of the one pair of connecting parts 63 and 64substantially corresponds to a distance between the axial end faces 44and 45 of the intermediate members 40 a and 40 b respectively. Bottomsurfaces and opening sides (an outer side of the cage 60) of the Ushaped forms of the connecting parts 63 and 64 are formed to be flat inparallel with the bottom surfaces opposite to the opening sides.

Further, one of end parts of the opening sides of the U shaped forms ofthe connecting parts 63 and 64 are respectively connected to the centralparts in the circumferential direction of the bent parts 61 c and 61 dof the circulating path forming member 61 and the other of the end partsare respectively connected to the central parts in the circumferentialdirection of the bent parts of the circulating path forming member 62.

Then, into the U shaped forms of the one pair of circulating pathforming members 61 and 62, the small diameter shaft parts 52 of therolling element 50 are inserted. In such a way, the rolling element 50is supported by the one pair of circulating path forming members 61 and62. Namely, the one pair of circulating path forming members 61 and 62support the rolling elements 50 so that the plurality of rollingelements 50 may circulate on the outer peripheries of the one pair ofintermediate members 40 a and 40 b. Here, the U shaped forms of the onepair of circulating path forming members 61 and 62 have small clearancesrelative to the outer peripheral surfaces of the small diameter shaftparts 52 of the rolling element 50. Further, under a state that thesmall diameter shaft parts 52 of the rolling element 50 are insertedinto the circulating path forming members 61 and 62, the cylindricalpart 51 of the rolling element 50 protrudes inside from the innerperipheral edges of the circulating path forming members 61 and 62 andprotrudes outside from the outer peripheral edges of the circulatingpath forming members 61 and 62.

Here, under a state that the one pair of intermediate members 40 a and40 b are arranged in the outer peripheral sides of the tripod shaft part22 and the one pair of intermediate members 40 a and 40 b are arrangedinside the cage 60, the straight line parts 61 a and 61 b (right andleft straight line parts in FIG. 8( a))(corresponding to a “firstcirculating path” of the present invention) are arranged between thepower transmission surfaces 42 of the intermediate members 40 a and 40 band the side surfaces of the raceway groove 11 so as to be substantiallyparallel to both the surfaces (in a following state). Namely, thecirculating path formed by the straight line parts 61 a and 61 b forms acirculating path when the rolling element 50 moves on the powertransmission surfaces 42. In at least one between the straight lineparts 61 a and 61 b, the power transmission surfaces 42 and the sidesurfaces of the raceway grooves 11, a clearance is formed.

Further, both end parts of the bent parts 61 c and 61 d (correspondingto a “second circulating path” of the present invention) of the one pairof circulating path forming members 61 and 62 are arranged so as to bedefined along the intermediate member introducing surfaces 43 of theintermediate members 40 a and 40 b. Namely, the circulating path formedby both the end parts of the bent parts 61 c and 61 d forms acirculating path when the rolling element 50 rolls on the intermediatemember introducing surfaces 43. The circulating path is connected to thecirculating path formed by the straight line parts 61 a and 61 b so asto be smoothly continuous to the circulating path formed by the straightline part 61 a and 61 h. Further, clearances are formed between both theend parts of the bent parts 61 c and 61 d forming the circulating pathand the intermediate member introducing surfaces 43. It is to beunderstood that clearances are formed between both the end parts of thebent parts 61 c and 61 d and the side surfaces of the raceway groove 11.

As described above, the power transmission surfaces 42 and theintermediate member introducing surfaces 43 of the one pair ofintermediate members 40 a and 40 b which form one side of the powertransmitting direction are configured so as to foul) clearances relativeto the circulating path forming members 61 and 62 of the cage 60.Namely, the one pair of intermediate members 40 a and 40 b are notregulated in the power transmitting direction relative to the one pairof circulating path forming members 61 and 62.

Further, a circulating path (corresponding to a “third circulating path”of the present invention) of the bent parts 61 c and 61 d of the onepair of circulating path forming members 61 and 62 which is connected tothe parts defined along the intermediate member introducing surfaces 43is smoothly and continuously connected to the circulating path definedalong the intermediate member introducing surfaces 43.

Then, in accordance with the relation between the foul's and theclearance of the axial end faces 44 and 45 of the intermediate members40 a and 40 b respectively and the forms and the clearance of the bottomsurfaces opposite to the opening sides of the U shaped forms of theconnecting parts 63 and 64, the intermediate members 40 a and 40 b areprovided between the connecting parts 63 and 64 so that the connectingparts 63 and 6 regulate a relative operation of the intermediate members40 a and 40 b in the axial direction (a vertical direction in FIG. 8(a)) of the outer ring 10. However, since the intermediate members 40 aand 40 b are not regulated in a radial direction (a vertical directionin FIG. 8( b)) of the outer ring 10 relative to the cage 60, theintermediate members 40 a and 40 b can move in the radial direction (thevertical direction in FIG. 8( b)). Namely, the cage 60 does not comeinto contact with the one pair of intermediate members 40 and the sidesurfaces of the raceway groove 11 in the power transmitting direction.

Nov, an operation of the above-described constant velocity joint 1 willbe described below. When the outer ring 10 having the one end sideconnected to the differential gear receives a power to rotate, thetripod shaft parts 22 respectively transmit the power through the rollerunits 30 respectively fitted to the raceway grooves 11 and theintermediate shaft connected to the tripod 20 rotates at constantvelocity. At this time, when the joint angle is not 0 deg, the tripod 20rotates on the intermediate shaft under a state that the tripod 20 isinclined by the joint angle relative to a section orthogonal to therotation axis of the outer ring 10. Accordingly, when viewing from theside surfaces of the raceway grooves 11, the tripod shaft parts 22 arereciprocated in the extending direction of the raceway grooves 11 inaccordance with the rotation of the outer ring 10 and the tripod 20 andoscillated relative to the raceway grooves 11.

Further, as described above, since the tripod 20 is inclined by thejoint angle relative to the section orthogonal to the rotation axis ofthe outer ring 10, an angle formed by the tripod shaft parts 22 seenfrom the direction of the rotation axis of the outer ring 10 changesdepending on a phase of the intermediate shaft. Accordingly, in order toinsert the three tripod shaft parts 22 respectively into the racewaygrooves 11, the rotation axis of the shaft connected to the tripod 20 iseccentrically rotated relatively to the rotation axis of the outer ring10. Accordingly, the end parts of the tripod shaft parts 22 arereciprocated in the radial direction of the outer ring 10 in accordancewith the rotation of the outer ring 10 and the tripod 20.

Here, the tripod contact surfaces 41 of the one pair of intermediatemembers 40 a and 40 b forming the roller unit 30 are fitted to thetripod shaft parts 22 so as to oscillate. Further, the one pair ofintermediate members 40 a and 40 b are regulated in the axial directionof the outer ring 10 by the cage 60 forming the roller unit 30. Further,the cage 60 is fitted to the raceway grooves 11. Accordingly, the cage60 is movable in the extending direction of the raceway grooves 11relative to the raceway grooves 11, however, an inclination to theraceway grooves 11 is substantially fixed. Then, the rolling elements 50circulate on the outer peripheries of the one pair of intermediatemembers 40 a and 40 b.

Accordingly, the rolling elements 50 roll between the power transmissionsurfaces 42 as members of a power transmission side of the intermediatemembers 40 a and 40 b and the side surfaces of the raceway grooves 11without generating a slide in the extending direction of the racewaygrooves 11 relative to the raceway grooves 11 and the power transmissionsurface 42. Thus, the generation of an induced thrust force can beprevented.

Further, the member of the one pair of intermediate members 40 a and 40b which receives the power through the plurality of rolling elements 50transmits the power to the tripod shaft parts 22 on which the tripodcontact surface 41 abuts. At this time, when the joint angle is appliedas described above, the tripod shaft parts 22 are reciprocated in theradial direction of the outer ring 10. Accordingly, since theintermediate member 40 a spherically fitted to the tripod shaft parts 22follows the tripod shaft parts 22, the intermediate member slides in theradial direction of the outer ring 10 relative to the rolling elements50. Thus, a load point in the power transmission surface 42 to which thepower is most applied is reciprocated in the axial direction of therolling elements 50. In accordance with the movement of the load point,an oscillating force is applied to the member of the power transmissionside of the one pair of intermediate members 40 a and 40 b as the memberof the power transmission side on a point where the rolling elements 50abut on the side surfaces of the raceway grooves 11 as a supportingpoint.

However, the one pair of intermediate members 40 a and 40 b areindependent respectively in the power transmission side and a backsurface side thereof. Thus, even when a load position is changed by thetripod shaft parts, which arises in the power transmission side, anoperation of the member of the power transmission side of the one pairof intermediate members 40 a and 40 b does not give an influence to anoperation of the intermediate member of the back surface side.Accordingly, the back surface side of the roller unit 30 can beprevented from applying a large force to the raceway grooves 11, so thatthe generation of the induced thrust force can be extremely reduced.Further, a clearance between the intermediate member 40 a (or 40 b) ofthe back surface side and the raceway grooves 11 does not need to beenlarged to prevent the generation of a rotation backlash.

Especially, the cage 60 is not regulated in the power transmittingdirection relative to the one pair of intermediate members 40. Thus, thecage 60 can prevent the rolling elements 50 from acting so as to apply aforce to the raceway grooves 11 of the outer ring 10 in the back surfaceside of a power transmission. Accordingly, the above-described mattercan reduce the occurrence of the induced thrust force in the backsurface side of the power transmission.

Further, in the one pair of intermediate members 40 a and 40 b, theintermediate member introducing surfaces 43 which are smoothlycontinuous to the power transmission surfaces 42 are formed to smoothlyguide the circulating rolling elements 50 to the power transmissionsurfaces 42 so as to come into contact therewith. In such a way, sincethe power transmission surfaces 42 of the power transmission members 40a and 40 b and the intermediate member introducing surfaces 43 whichallow the rolling elements 50 to enter the power transmission surfaces42 are formed with the same members, positions of the rolling elements50 entering the power transmission surfaces 42 can be stably arranged.

Further, the circulating paths formed by both the end parts of the bentparts 61 c and 61 d of the one pair of circulating path forming members61 and 62 are formed with configurations defined along the intermediatemember introducing surfaces 43. The circulating paths (the circulatingpaths connected to the connecting parts 63 and 64) of the circulatingpaths defined along the intermediate member introducing surfaces 43which are connected to opposite sides to the power transmission surfaces42 are smoothly and continuously connected to the circulating pathsdefined along the intermediate member introducing surfaces 43.

Here, since the intermediate member introducing surfaces 43 are notparts that transmit the power between the raceway grooves 11 and theintermediate member introducing surfaces, a greatly large load is notapplied to the rolling elements 50 moving on the intermediate memberintroducing surfaces 43. Therefore, the rolling elements 50 can beallowed to stably enter the circulating paths defined along theintermediate member introducing surfaces 43 from the circulating pathsto which the connecting parts 63 and 64 are connected. As a result, therolling elements 50 can be smoothly moved from the circulating paths towhich the connecting parts 63 and 64 are connected to the circulatingpaths defined along the intermediate member introducing surfaces 43, andfrom the circulating paths defined along the intermediate memberintroducing surfaces 43 to the circulating paths defined along the powertransmission surfaces 42.

Further, since the one pair of intermediate members 40 a and 40 b arespherically fitted to the tripod shaft parts 22 so as to be oscillated,a load (face pressure) per unit area of the intermediate members 40 aand 40 b can be reduced to improve the durability of the intermediatemembers 40 a and 40 b. Further, since the intermediate members 40 a and40 b follow the sliding tripod shaft parts 22, the positions thereof canbe determined relative to the tripod shaft parts 22 to stably transmitthe power. Further, since the one pair of intermediate members 40 a and40 b are arranged so as to sandwich the tripod shaft parts 22 betweenthem, the tripod contact surfaces 41 of the intermediate members 40 aand 40 b are respectively easily formed in entirely spherically recessedshapes. Accordingly, power transmission areas of the tripod shaft parts22 and the one pair of intermediate members 40 a and 40 can beincreased. Further, when the tripod shaft parts 22 come into angularcontact with the intermediate members 40 a and 40 b, two points of theangular contact are further spaced to be stabilized.

Since the rolling elements 50 have cylindrical needle shapes, theneedles abut on the side surfaces of the raceway grooves 11 of the outerring 10 in the axial direction of the cylinder to transmit the power.Thus, the roller unit 30 is low in its rotation backlash as a whole, sothat a stable power transmission can be realized.

Modification of First Exemplary Embodiment

In the above-described first exemplary embodiment, the tripod contactsurfaces 41 of e one pair of intermediate members 40 a and 40 b have thespherically recessed shapes. Otherwise, the tripod contact surfaces 41of the one pair of intermediate members 40 a and 40 b may be formed incylindrical surfaces.

In this case, other structures are the same as those of the firstexemplary embodiment. Namely, the one pair of intermediate members 40 aand 40 b are formed so that the tripod contact surfaces 41 thereof havethe cylindrical surfaces and arranged so as to sandwich tripod shaftparts 22 between them. Thus, the tripod shaft parts 22 and the one pairof intermediate members 40 can slide.

In such a structure, the tripod shaft parts 22 may have a range in whichthe tripod shaft parts 22 can slide enlarged relative to a roller unit30. Even when a joint angle is applied to increase an amount that thetripod shaft parts 22 slide, the above-described effects can be held anda power can be transmitted. Further, in accordance with theabove-described structure, a structure may be used that can suppress aslide between rolling elements 50 and the intermediate members 40 a and40 b.

Second Exemplary Embodiment

Now, a constant velocity joint 101 of a second exemplary embodiment willbe described by referring to FIG. 9 to FIG. 14. FIG. 9 is a radiallysectional view of a part of the constant velocity joint 101 of thesecond exemplary embodiment. FIG. 10 is a perspective view of a rollerunit 130. FIG. 11 is a perspective view of a cage 160. FIG. 12( a) is aplan view of the cage 160, FIG. 12( b) is a view of the cage 160 seenfrom a direction J and FIG. 12( c) is a sectional view of the cage 160taken along a line K-K (a diagram including a partial section of a majoraxis side). FIG. 13 is one perspective view of a pair of intermediatemembers 140. FIG. 14( a) is a front view of the intermediate member 140,FIG. 14( b) is a partly sectional view of the intermediate member 140taken along a line L-L, FIG. 14( c) is a diagram of the intermediatemember 140 seen from a direction M and FIG. 14( d) is a sectional viewof the intermediate member 140 taken along a line N-N.

As shown in FIG. 9 and FIG. 10, the constant velocity joint 101 includesan outer ring 110, a tripod 20 and a roller unit 130. Here, the constantvelocity joint 101 of the second exemplary embodiment is mainlydifferent in view of a point that the rolling element 50 of the constantvelocity joint 1 of the first exemplary embodiment is changed from theneedle to a spherical member. In accordance therewith, the forms of sidesurfaces of raceway grooves 111 of an outer ring 110 and configurationsof outer surfaces of one pair of intermediate members 140 are differentfrom those of the constant velocity joint 1 of the first exemplaryembodiment. Since the tripod 20 is the same as the tripod 20 of thefirst exemplary embodiment, a detailed explanation thereof will beomitted. Only different points will be described below.

The outer ring 110 is different from the outer ring 10 of the firstexemplary embodiment only in the forms of the side surfaces of theraceway grooves. As shown in FIG. 9, on the side surfaces at both sidesof the raceway grooves 111, recessed grooves are formed no as to definethe spherical surfaces of rolling elements 150 so that the rollingelements 150 formed with the spherical members may be positioned in theradial direction of the outer ring 110. Namely, in the recessed groovesin the side surfaces of the raceway grooves 111, a sectional form in theradial direction of the outer ring 110 is a circular arc form.

The roller unit 130 is formed in an annular shape as an entire shape asshown in FIG. 10 and arranged in an outer peripheral side of tripodshaft parts 22. The roller unit 130 includes an intermediate member 140,a plurality of rolling elements 150 and a cage 160.

The intermediate member 140 includes one pair of intermediate members140 a and 140 b. As shown in FIG. 13 and FIG. 14, the surface of each ofthe one pair of intermediate members 140 a and 140 b includes a tripodcontact surface 41, a power transmission surface 142, intermediatemember introducing surfaces 143 and axial end faces 44 and 45. Thetripod contact surface 41 and the axial end faces 44 and 45 are the sameas those of the first exemplary embodiment.

On the power transmission surface 142, a recessed groove is formed so asto define the spherical surface of the rolling element 150 as thespherical member. Further, on the intermediate member introducingsurfaces 143 formed at both sides adjacent to the power transmissionsurface 142, recessed grooves are formed which are similar to that ofthe power transmission surface 142. Other structures of the powertransmission surface 142 and the intermediate member introducingsurfaces 143 are the same as those of the first exemplary embodiment.

As shown in FIG. 10, the rolling element 150 is the spherical member anda plurality of rolling elements are arranged so as to circulate on anouter periphery of the intermediate member 140 as in the case of theneedle.

The cage 60 has an annular shape as an entire form similarly to the casethat the rolling element is the needle. While the circulating pathforming members 61 and 62 that form the cage 60 of the first exemplaryembodiment are respectively configured in U shaped forms, circulatingpath forming members 161 and 162 of the cage 160 of the second exemplaryembodiment are arranged so as to be opposed in the vertical direction inFIG. 9 and provided with circular arc recessed grooves so as to supportthe spherical rolling elements 150.

Now, an operation of the above-described constant velocity joint 101will be described below. Differently from the case that the rollingelement 150 is the needle, when the spherical surfaces of the rollingelements 150 respectively abut on the circular arc recessed grooves ofthe intermediate members 140 a and 140, both the members can oscillatewhen viewing from the axial direction of the outer ring 110.Accordingly, when a joint angle is taken, the intermediate members 140 aand 140 b oscillate relative to the tripod shaft parts 22 sliding in theaxial direction of the tripod when viewing from the axial direction ofthe outer ring 110.

The constant velocity joint 101 of the second exemplary embodimentconstructed as described above achieves the same effects as those by theconstant velocity joint 1 of the first exemplary embodiment. Further,the rolling element 150 as the spherical member is high in its rigidityand excellent in its circulating property. Further, the spherical memberhaving the small number of working processes is relatively easilyproduced and an attachment of the constant velocity joint 101 can besimplified. Further, since the rolling element 150 is formed with thespherical member, load points applied to members respectively are notbiased depending on the varying positional relation between the tripodshaft parts 22 and the raceway grooves 111 and a power can betransmitted.

Third Exemplary Embodiment

Now, a constant velocity joint 201 of a third exemplary embodiment willbe described below by referring to FIG. 15. FIG. 15 is a radiallysectional view of a part of the constant velocity joint 201 of the thirdexemplary embodiment. As shown in FIG. 15, the constant velocity joint201 includes an outer ring 110, a tripod 20 and a roller unit 230. Here,the constant velocity joint 201 of the third exemplary embodiment isdifferent in view of a point that the rolling element 50 of the constantvelocity joint 101 of the second exemplary embodiment is changed fromthe spherical member to a barrel shaped roller. Only different pointswill be described below.

Namely, the roller unit 230 includes an intermediate member 140, aplurality of rolling elements 250 and a cage 160. The rolling element250 is the barrel shaped roller and a plurality of rolling elements arearranged so as to circulate on an outer periphery of the intermediatemember 140 as in the case of the spherical member and the needle. Thebarrel shaped roller is the rolling element that has a pillar shape andin which a section cut in the direction orthogonal to the extendingdirection of the pillar is circular and a part corresponding to an outerperipheral surface in a section cut in the extending direction of thepillar has a circular arc protruding shape.

In accordance with such a structure, the bias of load pointsrespectively applied to the members during the transmission of a poweris prevented as in the rolling member 150 of the spherical member in thesecond exemplary embodiment and a width of the pillar in the directionorthogonal to the extending direction of the pillar can be decreasedmore than that of the spherical member. As a result, an entire part ofthe constant velocity joint 201 can be made to be compact.

Fourth Exemplary Embodiment

A constant velocity joint 301 of a fourth exemplary embodiment will bedescribed below by referring to FIG. 16. When the structure of theconstant velocity joint 1 of the first exemplary embodiment is set as abasic structure, in the constant velocity joint 301 of the fourthexemplary embodiment, an outer ring PCR (pitch circle radius) 302 and atripod PCR 303 are set so as to be different from each other. FIG. 16 isa radially sectional view of a part of the constant velocity joint 301of the fourth exemplary embodiment. Since the constant velocity joint301 of the fourth exemplary embodiment is substantially formed with thesame structure as that of the constant velocity joint I of the firstexemplary embodiment, the same reference numerals are respectively usedfor components.

As shown in FIG. 16, outer peripheral surfaces of tripod shaft parts 22have spherically protruding shapes. Under a position where a rotationaxis 13 of an outer ring coincides with a rotation axis 23 of anintermediate shaft, the tripod PCR 303 is set to be larger than theouter ring PCR 302.

In a rolling element 50 located between a power transmission surface 42and side surfaces of raceway grooves 11, the outer ring PCR 302indicates the shortest distance between an intersection 304 on a tripodaxis on a plane passing thorough the center of width of the rollingelement 50 in the axial direction of a tripod (a vertical direction inFIG. 16) and orthogonal to the tripod axis and the rotation axis 13 ofthe outer ring. The tripod PCR 303 indicates the shortest distancebetween a center of curvature 305 of the outer peripheral surfaces ofthe tripod shaft parts 22 and the rotation axis 23 of the intermediateshaft.

Now, by referring to FIG. 17 and FIG. 18, an explanation will be givenbelow. FIG. 17 is a diagram seen from an opening side of an outer ring10 in the constant velocity joint 301 to which a prescribed joint angleis applied. FIG. 18 is a diagram seen from the opening side of the outerring 10 in the constant velocity joint 301 to which a prescribed jointangle is applied. FIG. 19 is a graph showing a joint angle and a maximumand minimum moving amount of a load point for each offset amount. InFIG. 19, (a) shows an offset amount of 0 mm, (b) shows an offset amountof 0.1 mm, (c) shows an offset amount of 0.2 mm and (d) shows an offsetamount of 0.3 mm. The load point is a position in the radial directionof the outer ring of a position to which a load is applied during apower transmission between the tripod shaft parts 22 and intermediatemembers 40 a and 40 b.

As shown in FIG. 17 and FIG. 18, when the joint angle is applied, theload point moves depending on a rotation phase. Here, the load pointwhen the joint angle is 0 deg is set as a reference load point 306.

For instance, in FIG. 17, the rotation axis 23 of the intermediate shaftis applied as the joint angle in a rightward direction of FIG. 17. Underthis state, a tripod 20 rotates together with the intermediate shaft andone of the tripod shafts 22 is located in an upward direction of FIG.17. Then, as described above, the tripod 20 eccentrically rotatesrelative to the outer ring 10. This eccentric rotation causes a firstload point 307 to move outward in the radial direction of the outer ring10 from the reference load point 306 and to be located at a positionmost separating from the rotation axis 13 of the outer ring.

On the other hand, in FIG. 18, the rotation axis 23 of the intermediateshaft is applied as the joint angle in an upward direction of FIG. 18.Under this state, the tripod 20 rotates together with the intermediateshaft and one of the tripod shafts 22 is located in an upward directionof FIG. 18. Then, an eccentric rotation of the tripod 20 causes a secondload point 308 to move inward in the radial direction of the outer ring10 from the reference load point 306 and to be located at a positionclosest to the rotation axis 13 of the outer ring.

A moving amount of the first load point 307 from the reference loadpoint 306 is smaller than a moving amount of the second load point 308form the reference load point 306. If the outer ring PCR 302 is set tocoincide with the tripod PCR 303, a moving amount average of the loadpoints of the tripod shaft parts 22 applied to a roller unit 30 isbiased to a direction toward the rotation axis 13 of the outer ring.Accordingly, this causes a partial abrasion of the rolling elements 50to be increased.

Thus, the tripod PCR 303 is previously set (offset) to be larger thanthe outer ring PCR 302, so that the moving amount average of the loadpoints is located at a center of the thickness of the roller unit 30 andthe deviation of the load can be prevented. However, since the movingamounts of the first load point 307 and the second load point 308 fromthe reference load point 306 respectively depend on an applied jointangle, optimum offset amounts are different depending on the prescribedjoint angle. As shown in FIG. 19, when maximum values and minimum valuesof the moving load points are seen at the joint angles in the offsetamounts respectively, for instance, if the joint angle is 7 deg, it isrequested that the offset amount of 0.1 mm is optimum. Similarly, if thejoint angle is 10 deg, it is requested that the offset amount of 0.2 mmis optimum. If the joint angle is 13 deg, it is requested that theoffset amount of 0.3 mm is optimum respectively.

Accordingly, when the constant velocity joint is used, the offset amountis set depending on a supposed and ordinarily used joint angle. Thus,the increase of the partial abrasion of the rolling elements 50 can beprevented. As a result, the durability of the constant velocity jointcan be improved and vibration or noise can be reduced.

Fifth Exemplary Embodiment

Now, a constant velocity joint 401 of a fifth exemplary embodiment willbe described below by referring to FIG. 20 and FIG. 21. FIG. 20 is aradially sectional view of a part of the constant velocity joint 401 ofthe fifth exemplary embodiment. FIG. 21 is a graph showing a joint angleand a rotation backlash for each offset amount. In FIG. 21, (a) shows anoffset amount of 0 mm, (b) shows an offset amount of 0.2 mm, (c) showsan offset amount of 0.3 mm and (d) shows an offset amount of 0.6 mm.

A rolling element 50 is a spherical member. In this case, as describedin the fourth exemplary embodiment, when an outer ring PCR 302 is set tocoincide with a tripod PCR 303 as a result of an eccentric rotation of atripod 20, a moving amount average of load points is biased to adirection toward the rotation axis 13 of an outer ring. When the jointangle is 0 deg at which the bias does not arise, a rotation backlash isminimum. A problem arises that as the joint angle is more applied, therotation backlash is more increased.

Thus, as shown in FIG. 20, the tripod PCR 303 is previously set (offset)to be larger than the outer ring PCR 302 so that the rotation backlashcan be made to be minimum when a prescribed joint angle is applied toprevent the increase of the rotation backlash. However, since an amountof the rotation backlash depends on an applied joint angle, optimumoffset amounts are different depending on the prescribed joint angle. Asshown in FIG. 21, when the increases of the rotation backlash are seenat the joint angles in the offset amounts respectively, for instance, ifthe joint angle is 6 deg, it is requested that the offset amount of 0.2mm is optimum. Similarly, if the joint angle is 7 deg, it is requestedthat the offset amount of 0.3 mm is optimum. If the joint angle is 10deg, it is requested that the offset amount of 0.6 min is optimumrespectively.

Accordingly, when the constant velocity joint is used, the offset amountis set depending on a supposed and ordinarily used joint angle. Thus,the increase of the rotation backlash of the rolling elements 50 can beprevented. As a result, the durability of the constant velocity jointcan be improved and vibration or noise can be reduced. When the rollingelement is a barrel shaped roller, when the tripod PCR 303 is set asdescribed above, the same effects can be obtained.

Sixth Exemplary Embodiment

A constant velocity joint 501 of a sixth exemplary embodiment will bedescribed by using FIGS. 22 to 26. The same members as those of thefirst exemplary embodiment are designated by the same reference numeralsand an explanation thereof will be omitted.

As shown in FIGS. 24 and 25( a), a cage 560 has an annular shape as anentire form. The cage 560 includes a pair of circulating path formingmembers 561 and 562 that form a circulating path of rolling elements 50and a pair of connecting parts 63 and 64. The one pair of circulatingpath forming members 561 and 562 are located in peripheral edges of thecage 560 and have elliptic forms. The one pair of circulating pathforming members 561 and 562 have such forms as to surround one pair ofintermediate members 540 a and 540 b.

As shown in FIG. 24, the circulating path forming member 561 includes afirst circulating path 561 a, a second circulating path 561 b, a thirdcirculating path 561 c and a fourth circulating path 561 d. The firstcirculating path 561 a and the second circulating path 561 b are formedwith opposed straight lines.

The third circulating path 561 c connects one ends of the firstcirculating path 561 a and the second circulating path 561 b togetherand is formed in a bent shape protruding in the direction toward tripodshaft parts. More specifically, the third circulating path 561 c isformed with a substantially W shaped curve when the third circulatingpath is seen from the axial direction of the cage 560. Tangential linesat both ends of the third circulating path 561 c are respectively formedso as to substantially coincide with tangential lines of the one ends ofthe first circulating path 561 a and the second circulating path 561 b.A central part in the circumferential direction of the third circulatingpath 561 c (the same as a central part in the circumferential directionof an outer ring 10) is most bent in a protruding shape in the directiontoward the tripod shaft parts. This bent part in a protruding shape isformed in a circular arc shape. A curvature radius of the circular arcshape is set to a radius substantially the same as an outside diameterof a part of an intermediate shaft that comes close to the cage 560 or aradius smaller than the outside diameter. Further, two trough parts ofthe W shape of the third circulating path 561 c are also formed incircular arc shapes.

The fourth circulating path 561 d is formed with a fourth semi-circulararc shaped circulating path 561 d connects the other ends of the firstcirculating path 561 a and the second circulating path 561 b together.Further, the other circulating path forming member 562 includes, likethe above-described circulating path forming member 561, first, second,third and fourth circulating paths 562 a, 562 b, 562 c and 562 d.

Further, the third circulating path 561 c is bent in a protruding shapein the direction toward the tripod shaft parts (upward in FIG. 25( a)).However, as shown in FIG. 25( c), the third circulating path is not bentin the axial direction of the cage 560 (in a radial direction of theouter ring 10 under a state that the cage 560 is attached to the outerring 10) (a transverse direction in FIG. 25( c)). Namely, a circulatinglocus formed by the third circulating paths 561 c and 562 c is a locusin the same plane having no component in the axial direction of atripod.

Further, the one pair of circulating path forming members 561 and 562are respectively configured in U shaped sectional forms into which asmall diameter shaft part 52 of the rolling element 50 can be insertedand with which a cylindrical part 51 is engaged. Namely, a width (adistance between an inner peripheral edge and an outer peripheral edge)of the one pair of circulating path forming members 561 and 562 isformed to be smaller than a maximum diameter of the cylindrical part 51of the rolling element 50. Under a state that the U shaped opening sidesof the circulating path forming members 561 and 562 are spaced by adistance longer than the axial length of the cylindrical part 51 of therolling element 50, the U shaped opening sides are provided so as to beopposed to each other. A maximum width between the one pair ofcirculating path forming members 561 and 562 in an opposing direction isset to be slightly smaller than the width of the side surfaces ofraceway grooves 11. Namely, the cage 560 is provided so that aninclination thereof may be regulated relative to the raceway grooves 11by groove bottom surfaces and the engaging protrusions 12 of the racewaygrooves 11 and the cage may be inserted into the raceway grooves 11.

The one pair of connecting parts 63 and 64 respectively connect togethercentral parts (upper and lower end parts in FIG. 25( a)) in thecircumferential direction of the third circulating path 561 c and thefourth circulating path 561 d of the one pair of circulating pathforming members 561 and 562. Namely, as shown in FIG. 25( c), apartbetween the one pair of circulating path forming members 561 and 562 isopened in a part excluding the connecting parts 63 and 64.

The connecting parts 63 and 64 are configured in U shaped forms openedoutward the cage 560. Bottom surfaces opposite to opening sides of the Ushaped forms of the connecting parts 63 and 64 (an inner side of thecage 560) are formed to be flat. The bottom surfaces opposite to theopening sides of the U shaped forms of the one pair of connecting parts63 and 64 are provided so as to be parallel and opposed to each other. Aclearance between the bottom surfaces opposite to the opening sides ofthe U shaped forms of the one pair of connecting parts 63 and 64substantially coincide with a distance between axial end faces 44 and 45of the intermediate members 40 a and 40 b respectively. Bottom surfacesand opening sides (an outer side of the cage 560) of the U shaped formsof the connecting parts 63 and 64 are formed to be flat in parallel withthe bottom surfaces opposite to the opening sides.

Further, one of end parts of the opening sides of the U shaped forms ofthe connecting parts 63 and 64 are respectively connected to the centralparts in the circumferential direction of the third circulating path 561c and the fourth circulating path 561 d of the circulating path formingmember 561 and the other of the end parts are respectively connected tothe central parts in the circumferential direction of the thirdcirculating path 562 c and the fourth circulating path 562 d of thecirculating path forming member 562.

Then, into the U shaped forms of the one pair of circulating pathforming members 561 and 562, the small diameter shaft parts 52 of therolling element 50 are inserted. In such a way, the rolling element 50is supported by the one pair of circulating path forming members 561 and562. Namely, the one pair of circulating path forming members 561 and562 support the rolling elements 50 so that the plurality of rollingelements 50 may circulate on the outer peripheries of the one pair ofintermediate members 40 a and 40 b. Here, the U shaped forms of the onepair of circulating path forming members 561 and 562 have smallclearances relative to the outer peripheral surfaces of the smalldiameter shaft parts 52 of the rolling element 50. Further, under astate that the small diameter shaft parts 52 of the rolling element 50are inserted into the circulating path forming members 561 and 562, thecylindrical part 51 of the rolling element 50 protrudes inside from theinner peripheral edges of the circulating path forming members 561 and562 and protrudes outside from the outer peripheral edges of thecirculating path forming members 561 and 562.

Here, under a state that the one pair of intermediate members 40 a and40 b are arranged in the outer peripheral sides of the tripod shaftparts 22 and the one pair of intermediate members 40 a and 40 b arearranged inside the cage 560, the first circulating paths 561 a and 562a and the second circulating paths 561 b and 562 b (right and leftstraight line parts in FIG. 25( a)) of the circulating path formingmembers 561 and 562 are respectively arranged between power transmissionsurfaces 42 of the intermediate members 40 a and 40 b and the sidesurfaces of the raceway groove 11 so as to be substantially parallel toboth the surfaces (in a following state). Namely, the circulating pathsformed by the first circulating paths 561 a and 562 a and the secondcirculating paths 561 b and 562 b form circulating paths when therolling element 50 moves on the power transmission surfaces 42. Further,at least in one between the first circulating paths 561 a and 562 a, thesecond circulating paths 561 b and 562 b, the power transmissionsurfaces 42 and the side surfaces of the raceway grooves 11, a clearanceis formed.

Further, both end parts of the third circulating paths 561 c and 562 cand the fourth circulating paths 561 d and 562 d of the one pair ofcirculating path forming members 561 and 562 are arranged so as todefine introducing surfaces formed in both the end parts of the powertransmission surfaces 42 of the intermediate members 40 a and 40 b.Namely, the circulating paths formed by both the end parts of the thirdcirculating paths 561 c and 562 c and the fourth circulating paths 561 dand 562 d form circulating paths when the rolling element 50 moves onthe introducing surfaces. The circulating paths are connected to thecirculating paths formed by the first circulating paths 561 a and 562 aand the second circulating paths 561 b and 562 b so as to be smoothlycontinuous thereto. Further, clearances are formed between both the endparts of the third circulating paths 561 c and 562 c and the fourthcirculating paths 561 d and 562 d that form the circulating paths andthe introducing surfaces. It is to be understood that clearances areformed between both the end parts of the third circulating paths 561 cand 562 c and the fourth circulating paths 561 d and 562 d that form thecirculating paths and the side surfaces of the raceway grooves 11.

When the tripod shaft parts 22 are reciprocated in the extendingdirection of the raceway grooves 11, a roller unit 530 arranged in anouter peripheral side of the tripod shaft parts 22 is also reciprocated.In the reciprocating movement of the roller unit 530, when the rollerunit 530 is located at a position of a most interior side of the outerring 10, the intermediate shaft comes closest to the cage 560 of theroller unit 530. Here, when the cage 560 interferes with theintermediate shaft at a prescribed joint angle, an angle immediatelybefore the interference arises is a maximum joint angle which can betaken by the outer ring 10 and the intermediate shaft.

Here, the central part in the circumferential direction of the thirdcirculating paths 561 c and 562 c (the same as the central part in thecircumferential direction of the outer ring 10) is most bent in theprotruding shape in the direction toward the tripod shaft parts. Thus,as shown in FIG. 26, since, an end part of the roller unit 530 in anopening side of the outer ring 10 is moved more to an interior side ofthe outer ring 10 than a usual position, the intermediate shaft can takethe more the angle. Further, the bent shape of the cage 560 is formed ina circular arc recessed shape corresponding to an outer peripheralsurface of the intermediate shaft which comes close to the cage 560 whenthe intermediate shaft is bent with respect to the rotation axis of theouter ring 10. As a result of these things, the maximum joint angle canbe increased. Namely, in order to reduce a width of the roller unit 530in the direction of the rotation axis of the outer ring 10, a block fortransmitting a power is not shortened, the outside diameter of the outerring 10 is not enlarged, and a function can be maintained forsufficiently transmitting the power and the maximum joint angle can beincreased.

Modification of Sixth Exemplary Embodiment

In the above-described sixth exemplary embodiment, the fourthcirculating paths 561 d and 562 d of the cage 560 have semi-circular arcshapes. However, the cage is not limited to this form and may have abelow-described form. A cage 660 of a modification of the sixthexemplary embodiment will be described by referring to FIG. 27. FIG. 27is a plan view of the cage 660 as the modification of the sixthexemplary embodiment.

As shown in FIG. 27, the cage 660 includes a pair of circulating pathfowling members 661 and 662 that form a circulating path of rollingelements 50 and a pair of connecting parts 563 and 564. Fourthcirculating paths 661 d and 662 d of the cage 660 formed by the one pairof circulating path forming members 661 and 662 are configured in bentshapes protruding in the direction coining close to tripod shaft parts.More specifically, the fourth circulating paths 661 d and 662 d areformed with substantially W shaped curves as shown in FIG. 27 when thefourth circulating paths are seen from the axial direction of the cage660. First to third circulating paths 561 a to 561 c and 562 a to 562 care the same as those of the sixth exemplary embodiment. That is, thecage 660 is formed in a symmetrical shape relative to the tripod shaftparts 22 as a whole.

Additionally, an intermediate member 40 is not formed with separatemembers so as to form a pair and may be formed as an integral member. Inthis case, other structures are the same as those of the sixth exemplaryembodiment. Namely, the intermediate member 40 as the integral member isarranged so as to cover the outer peripheral surfaces of the tripodshaft parts 22 and the cage 660 is arranged outside the intermediatemember. Thus, the tripod shaft parts 22 and the intermediate member 40as the integral member can slide.

In such a way, when the cage 660 is formed in a symmetrical shape,between the third circulating paths 561 c and 562 c and the fourthcirculating paths 561 d and 562 d, substantially, there is nodifference. Accordingly, when a constant velocity joint 501 is attached,a direction that a roller unit 30 including the cage 660 is insertedinto raceway grooves 11 of an outer ring 10 does not need to beconsidered, so that an erroneous attachment can be prevented.

Further, since the intermediate member 40 can interrupt an operation ofa power transmission to a back surface side of the power transmission,the one pair of intermediate members formed with the separate membersare preferably used, however, when the intermediate member is not formedwith the separate members, but formed with the integral member, effectsof the present invention are also achieved.

Seventh Exemplary Embodiment

A constant velocity joint of a seventh exemplary embodiment will bedescribed by referring to FIG. 28 to FIG. 31. Parts corresponding tothose of the secondary exemplary embodiment are designated by the samereference numerals and an explanation thereof will be omitted.

The roller unit 530 of the sixth exemplary embodiment and a roller unit730 of the seventh exemplary embodiment are different from each othermainly view of three points. A first point resides in that a rollingelement 50 is changed to a spherical member from a needle. A secondpoint resides in that a bending direction of the bent part in aprotruding shape in the third circulating paths 561 c and 562 c of thecage 560 is changed to an outward direction in the radial direction ofan outer ring from the direction toward the tripod shaft parts. A thirdpoint resides in that a width of an opening part in the thirdcirculating paths 561 c and 562 c and the fourth circulating paths 561 dand 562 d is set to be smaller than a width of an opening part in thefirst circulating paths 561 a and 562 a and the second circulatingpaths.

In accordance with the change of the first point, the forms of sidesurfaces of raceway grooves 111 of an outer ring 110, configurations ofouter surfaces of one pair of intermediate members 140 and forms ofparts of a cage 160 for supporting a rolling element 150 are differentfrom those of the constant velocity joint 501 of the sixth exemplaryembodiment.

A cage 760 has an annular shape as an entire form similarly to the casethat the rolling element is the needle as shown in FIG. 30 and FIG. 31.While the circulating path forming members 561 and 562 that form thecage 560 of the sixth exemplary embodiment are respectively configuredin the U shaped forms, circulating path forming members 761 and 762 ofthe cage 760 of the seventh exemplary embodiment are arranged so as tobe opposed in the vertical direction in FIG. 28 and provided withcircular arc recessed grooves so as to support the spherical rollingelements 150.

A third circulating path 761 c connects one ends of a first circulatingpath 761 a and a second circulating path 761 b together and is formedwith a bent shape protruding outward in the radial direction of theouter ring. More specifically, the third circulating path 761 c isinclined outward in the radial direction of the pouter ring on theabove-described one end as a supporting point when the cage 760 is seenfrom a side surface (in a direction orthogonal to an axis of the cage760 with the first circulating path 761 a set in a transversedirection). A central part of the third circulating path 761 c in thecircumferential direction is most bent in a protruding shape outward inthe radial direction of the outer ring. Further, a third circulatingpath 762 c of the circulating path forming member 762 is formed with abent shape protruding outward in the radial direction of the outer ringso that a width of the third circulating path 761 c and the circulatingpath opposed thereto is fixed.

Now, an operation of the above-described constant velocity joint 701will be described below. A circulating path is formed so as to be bentin a protruding shape outward in the radial direction of the outer ringin the third circulating paths 761 c and 762 c, which is different fromthe case that the rolling element 150 is the needle. Thus, when therolling element 150 is discharged from a power transmitting block, therolling element is circulated so as to come close to bottom surfaces ofthe raceway grooves 111 toward the central parts of the thirdcirculating paths 761 c and 762 c in the circumferential direction.Then, after the rolling element passes thorough the central parts in thecircumferential direction, the rolling element is circulated to enteraback surface side of the power transmitting block. Further, the openingpart in the third circulating paths 761 c and 762 c and the fourthcirculating paths 761 d and 762 d is set to be narrower than the openingpart in the first circulating paths 761 a and 762 b and the secondcirculating paths 761 b and 762 b.

As described above, in the constant velocity joint 701 of the seventhexemplary embodiment, the central parts of the third circulating paths761 c and 762 c in the circumferential direction are most bent inprotruding shapes outward in the radial direction of the outer ring.Further, the bent shape of the cage 760 is formed in a circular arcrecessed shape corresponding to an outer peripheral surface of anintermediate shaft which comes close to the cage 760 when theintermediate shaft is bent with respect to the rotation axis of theouter ring 110. As a result of these things, a maximum joint angle canbe increased. Namely, in order to reduce a width of the roller unit 730in the direction of the rotation axis of the outer ring 110, a block fortransmitting a power is not shortened, the outside diameter of the outerring 110 is not enlarged, and a function can be maintained forsufficiently transmitting the power and a maximum joint angle can beincreased.

Further, the rolling element 150 as the spherical member is high in itsrigidity and excellent in its circulating property. Further, thespherical member having the small number of working processes isrelatively easily produced and an attachment of the constant velocityjoint 701 can be simplified.

Further, since the width of the opening parts in the third circulatingpaths 761 c and 762 c and the fourth circulating paths 761 d and 762 dare set to be narrow, even when a large inertia force is generated inthe rolling element 150, the rolling element 150 can be prevented fromfalling from the cage 760. Further, since the first, second, third andfourth circulating paths 761 a, 762 a, 761 b, 762 b, 761 c, 762 c and761 d and 762 d have opening parts in outer peripheral sides over allthe circumference, under a state that the constant velocity joint 701 isattached, the state of the rolling element 150 can be visuallyrecognized and lubricant can be assuredly allowed to adhere to therolling element 150 to ensure a good circulation of the rolling elements150.

When the cage 760 is formed in a symmetrical shape with respect totripod shaft parts 22, between the third circulating paths 761 c and 762c and the fourth circulating paths 761 d and 762 d, substantially, thereis no difference. Accordingly, when the constant velocity joint 701 isattached, a direction that the roller unit 730 including the cage 760 isinserted into the raceway grooves 111 of the outer ring 110 does notneed to be considered, so that an erroneous attachment can be prevented.

Modification of Seventh Exemplary Embodiment

In the constant velocity joint 701 of the seventh exemplary embodiment,the third circulating paths 761 c and 762 c are bent in protrudingshapes outward in the radial direction of the outer ring 110. In thesixth exemplary embodiment, the third circulating paths 561 c and 562 care bent in protruding shapes in the direction toward the tripod shaftparts. Thus, as a modification of the seventh exemplary embodiment, thethird circulating paths 761 c and 762 c may be bent in protruding shapesoutward in the radial direction of the outer ring 110 and bent inprotruding shapes in the direction toward the tripod shaft parts.

Eighth Exemplary Embodiment

A constant velocity joint of an eighth exemplary embodiment will bedescribed by referring to FIG. 32 and FIG. 33. FIG. 30 is a perspectiveview of a part in an attached state of a constant velocity joint 801 ofan eighth exemplary embodiment. FIG. 33 is a perspective view of a cage860.

As shown in FIG. 32, the constant velocity joint 801 includes thestructure of the constant velocity joint 501 of the sixth exemplaryembodiment as a base. The seventh exemplary embodiment is different inview of a point that the third circulating paths 761 c and 762 c and thefourth circulating paths 761 d and 762 d of the cage 760 of the seventhexemplary embodiment are not bent in protruding shapes outward in theradial direction of an outer ring nor bent in protruding shapes in thedirection toward tripod shaft parts. Now, only a different point will bedescribed below.

A roller unit 830 includes an intermediate member 140, a plurality ofrolling elements 150 and a cage 860. As shown in FIG. 32 and FIG. 33,the cage 860 is configured in an elliptic shape as an entire shape byfirst, second, third and fourth circulating paths 861 a, 862 a, 861 b,862 b, 861 c, 862 c and 861 d and 862 d and does not have a bent partprotruding outward in the radial direction of an outer ring nor in thedirection toward tripod shaft parts. Further, similarly to the cage 760of the seventh exemplary embodiment, a width of opening parts in thethird circulating paths 861 c and 862 c and the fourth circulating paths861 d and 862 d are set to be narrower than a width of an opening partin the first circulating paths 861 a and 862 a and the secondcirculating paths 861 b and 862 b. Further, the cage 860 is formedsymmetrically with respect to the tripod shaft parts 22.

In the constant velocity joint 801 of the eighth exemplary embodimentconstructed as described above, since the first, second, third andfourth circulating paths 861 a, 862 a, 861 b, 862 b, 861 c, 862 c and861 d and 862 d have opening parts in outer peripheral sides over allthe circumference, under a state that the constant velocity joint 801 isattached, the state of the rolling element 150 can be visuallyrecognized and lubricant can be assuredly allowed to adhere to therolling element 150 to ensure a good circulation of the rolling elements150. Further, even when the opening parts are provided, the width of theopening parts is properly set so that the rolling element 150 may beassuredly prevented from falling from the cage 860. Further, since thecage 860 is formed in a symmetrical shape with respect to the tripodshaft parts, during an attachment of the constant velocity joint 801, adirection that the roller unit 830 including the cage 860 is insertedinto raceway grooves 111 of an outer ring 110 does not need to beconsidered, so that an erroneous attachment can be prevented.

Ninth Exemplary Embodiment

A constant velocity joint 901 of a ninth exemplary embodiment will bedescribed by referring FIGS. 34 to 39. The same parts as those of thefirst exemplary embodiment are designated by the same reference numeralsand an explanation thereof will be omitted. FIG. 34 is a perspectiveview of a roller unit 930. FIG. 35( a) is a plan view of the roller unit930, FIG. 35( b) is a sectional view of the roller unit 930 taken alonga line A-A (a sectional view of a minor axis side) and FIG. 35( c) is apartly sectional view of the roller unit 930 taken along a line B-B (adiagram including a partial section of a major axis side). FIG. 36 isone perspective view of a pair of intermediate members 940. FIG. 37( a)is a front view of the intermediate member 940, FIG. 37( b) is a sideview of the intermediate member 940 and FIG. 37( c) is a view of theintermediate member 940 seen from a direction C. FIG. 38 is aperspective view of a cage 960. FIG. 39( a) is a plan view of the cage960, FIG. 39( b) is a sectional view of the cage 960 taken along a lineD-D (a sectional view of a minor axis side) and FIG. 39( c) is asectional view of the cage 960 taken along a line E-E (a diagramincluding a partial section of a major axis side).

An outer form of an intermediate member 940 is configured substantiallyin a rectangular shape as an entire form. Further, when the intermediatemember 940 is observed as a whole, a part corresponding to a circularhole is formed in a center of the intermediate member 940. A center X1of the circular hole is located at a position shifted by W1 to anopening side of an outer ring 10 from a central part X2 of a width W2 inthe direction of a rotation axis of the outer ring 10 in theintermediate member 940. The center X1 of the circular hole is aposition of a central axis (a tripod axis) of tripod shaft parts 22 at aposition of a joint angle of 0 deg. Further, the center X1 of thecircular hole is located at a central part of a width W5 in thedirection of the rotation axis of the outer ring 10 in below-describedintermediate members 940 a and 940 b. Further, the central part X2 ofthe width W2 coincides with a central part of a width W3 in thedirection of the rotation axis of the outer ring 10 in a below-describedpower transmission surface 942 and coincides with a central part of awidth W4 in the direction of the rotation axis of the outer ring 10 in abelow-described cage 960.

The intermediate member 940 includes a pair of members 940 a and 940 b.The one pair intermediate members 940 a and 940 b are formed by separatemembers so as to have symmetrical forms relative to a plane passingthorough the tripod axis and a rotation axis of an intermediate shaftand respectively independent. The one pair of intermediate members 940 aand 940 b are arranged, as in the first exemplary embodiment shown inFIG. 2, so as to sandwich the tripod shaft parts 22 from both sides ofside surfaces of raceway grooves 11. Namely, both the intermediatemembers 940 a and 940 b are arranged so as to sandwich the tripod shaftparts 22 from both sides in a power transmitting direction (a directionon the rotation axis of the outer ring or on the rotation axis of theintermediate shaft). The one pair of intermediate members 940 a and 940b are provided so as to oscillate in the direction of the rotation axisof the outer ring 10 relative to the tripod shaft parts 22 and oscillatein the circumferential direction of the outer ring 10.

A detailed form of each of the intermediate members 940 a and 940 b willbe described by referring to FIG. 36 and FIGS. 37( a) to 37(c). Thesurface of each of the intermediate members 940 a and 940 b includes atripod contact surface 941, a power transmission surface 942 and axialend faces 944 and 945. Here, when the one pair of intermediate members940 a and 940 b are seen as one body, the tripod contact surfaces 941form an inner surface and the power transmission surfaces 42 and theaxial end faces 944 and 945 form an outer surface.

The tripod contact surface 941 is formed in a partly sphericallyrecessed shape to come into contact with the tripod shaft parts 22 so asto oscillate in the axial direction of the outer ring 10 and in thecircumferential direction of the outer ring 10. A vertical width of thetripod contact surface 941 in FIG. 37( b) (a width in the axialdirection of the outer ring 10 in the intermediate member 940) is W5. Acenter of a spherical surface in the tripod contact surface 941 islocated at a center of a transverse width (the thickness of theintermediate member 940) of the tripod contact surface 941 shown in FIG.37( a) and shifted downward from a center of a vertical width (a widthin the axial direction of the outer ring 10 in the intermediate member940) shown in FIG. 37( b). Namely, the center of the spherical surfacein the tripod contact surface 941 is located on X1 in FIG. 37( b). TheX1 coincides with the central axis X1 of the tripod shaft parts 22 atthe joint angle of 0 deg as described in FIG. 35.

The power transmission surface 942 is provided in aback surface side ofthe tripod contact surface 941, that is, in the right side in FIG. 37(b). The power transmission surface 942 is formed in a planar andrectangular shape. The intermediate members 940 a and 940 b arerespectively arranged so that the power transmission surfaces 942 areparallel to the side surfaces of the raceway grooves 11. Namely, under aposition that the rotation axis of the outer ring 10 coincides with therotation axis of the intermediate shaft (a joint angle of 0 deg), thepower transmission surfaces 942 are parallel to the plane passingthorough the central axis of the tripod shaft parts 22 and the rotationaxis of the intermediate shaft. Further, the power transmission surface942 is located at a central part in the vertical direction shown in FIG.37( b) and has a width about ⅔ times as long as the vertical width W2 ofthe intermediate members 940 a and 940 b shown in FIG. 37( b). Namely,in the back surface side of the deepest part of the tripod contactsurface 941, the power transmission surface 942 is located. A center inthe vertical width W3 in the power transmission surface 942 in FIG. 37(b) is located on X2 in FIG. 37( b). Namely, the X2 is shifted by W1 fromthe center X1 of the spherical surface in the tripod contact surface 41.Further, the power transmission surface 942 has a range where the powertransmission surface may come into contact with a plurality of rollingelements 50 (three to four rolling elements in this exemplaryembodiment).

The axial end faces 944 and 945 are parts located at both ends in upperand lower parts in FIG. 37 b). Both the axial end faces 944 and 945 areformed with planes orthogonal to the power transmission surface 942.Namely, the axial end faces 944 and 945 are formed with planesorthogonal to the side surfaces of the raceway grooves 11. A clearancebetween the axial end faces 944 and 945 is W2. That is, the clearancecorresponds to a longitudinal width of the intermediate members 940 aand 940 b. A central part of the clearance W2 of the axial end faces 944and 945 is located on X2 in FIG. 37( b).

A circulating path forming member 961 includes opposed straight lineparts 961 a and 961 b and semi-circular arc shaped bent parts 961 c and961 d for connecting the straight line parts 961 a and 961 b. Further,another circulating path forming member 962 includes straight line parts962 a and 962 b and bent parts 962 c and 962 d similarly to theabove-described circulating path forming member 961.

A vertical width (a width in the axial direction of the outer ring 10 inthe cage 960) in the circulating path forming members 961 and 962 inFIG. 39( a) is W4. A central part of the width W4 is located on X2 shownin FIG. 39( b).

One pair of connecting parts 63 and 64 respectively connect togethercentral parts (upper and lower end parts in FIG. 39( a)) in thecircumferential direction of the bent parts 961 c and 961 d, 962 c and962 d of the one pair of circulating path forming members 961 and 962.Namely, as shown in FIG. 39( c), a part between the one pair ofcirculating path forming members 961 and 962 is opened except theconnecting parts 63 and 64.

The connecting parts 63 and 64 are configured in U shaped forms openedoutward the cage 960. Bottom surfaces opposite to opening sides of the Ushaped forms of the connecting parts 63 and 64 (an inner side of thecage 960) are formed to be flat. The bottom surfaces opposite to theopening sides of the U shaped forms of the one pair of connecting parts63 and 64 are provided so as to be parallel and opposed to each other. Aclearance between the bottom surfaces opposite to the opening sides ofthe U shaped forms of the one pair of connecting parts 63 and 64substantially coincides with a distance between the axial end faces 944and 945 of the intermediate members 940 a and 940 b respectively. Bottomsurfaces and opening sides (an outer side of the cage 960) of the Ushaped forms of the connecting parts 63 and 64 are formed to be flat inparallel with the bottom surfaces opposite to the opening sides of the Ushaped fowls.

Further, one of end parts of the opening sides of the U shaped forms ofthe connecting parts 63 and 64 are respectively connected to the centralparts in the circumferential direction of the bent parts 961 c and 961 dof the circulating path forming member 961 and the other of the endparts are respectively connected to the central parts in thecircumferential direction of the bent parts 962 c and 962 d of thecirculating path forming member 962.

Further, both end parts of the bent parts 961 c and 961 d, 962 c and 962d of the one pair of circulating path forming members 961 and 962 arearranged so as to define introducing surfaces formed on both end partsof the power transmission surfaces 942 of the intermediate members 940 aand 940 b. Namely, the circulating paths formed by both the end parts ofthe bent parts 961 c and 961 d, 962 c and 962 d form circulating pathswhen the rolling elements 50 move on the introducing surfaces. Thecirculating paths are connected to the circulating paths formed by thestraight line parts 961 a, 961 b, 962 a and 962 b so as to be smoothlycontinuous to thereto. Further, clearances are formed between both theend parts of the bent parts 961 c, 961 d, 962 c and 962 d forming thecirculating paths and the introducing surfaces. It is to be understoodthat clearances are formed between both the end parts of the bent parts961 c, 961 d, 962 c and 962 d forming the circulating paths and the sidesurfaces of the raceway grooves 11.

Now, an operation of the above-described constant velocity joint 901will be described by referring to FIG. 40. FIG. 40 is a side viewshowing a state that a joint angle is taken and the outer ring 10 isremoved for the purpose of a simple explanation in the attached constantvelocity joint 901. In FIG. 40, a left side shows an opening side of theouter ring 10 and a right side shows an interior side of the outer ring10.

When the tripod shaft parts 22 are reciprocated in the extendingdirection of the raceway grooves 11, a roller unit 930 arranged in anouter peripheral side of the tripod shaft parts 22 is also reciprocated.In the reciprocating movement of the roller unit 930, when the rollerunit 930 is located at a position of a most interior side of the outerring 10 as shown in FIG. 40, the intermediate shaft comes closest to thecage 960 of the roller unit 930. Here, when the cage 960 interferes withthe intermediate shaft at a prescribed joint angle, an angle immediatelybefore the interference arises is a maximum joint angle which can betaken by the outer ring 10 and the intermediate shaft.

Here, the center X1 of the part of the one pair of intermediate members940 corresponding to the circular hole is shifted by W1 to the openingside of the outer ring 10 from the central part X2 in a width W6 of theroller unit 930 in the axial direction of the outer ring, the width W4of the cage 960 in the axial direction of the outer ring, the width W2of the intermediate members 940 a and 940 b in the axial direction ofthe outer ring and the width W3 of the power transmission surface 942 inthe axial direction of the outer ring. Accordingly, the roller unit 930is located to be entirely shifted by W1 to the interior side of theouter ring 10 from the central axis X1 of the tripod shaft parts 22.Thus, as shown in FIG. 40, since the cage 960 located in the outermostside of the roller unit 30 moves to the interior side of the outer ring10, the intermediate shaft can take the more an angle.

Modification of Ninth Exemplary Embodiment

In the above-described ninth exemplary embodiment, the tripod contactsurfaces 941 of the one pair of intermediate members 940 a and 940 bhave the spherically recessed shapes. Otherwise, the tripod contactsurfaces 941 of the one pair of intermediate members 940 a and 940 b maybe formed in cylindrical surfaces. Additionally, the intermediate member940 is not formed with separate members so as to have a pair, but may beintegrally formed. Namely, the integrally formed intermediate member 940is arranged so as to cover the tripod shaft parts 22 and the cage 960 isarranged outside the intermediate member. Thus, the intermediate memberformed integrally with the tripod shaft parts 22 can slide.

In such a structure, the tripod shaft parts 22 may have a range in whichthe tripod shaft parts 22 can slide enlarged relative to the roller unit930. Even when a joint angle is applied to increase an amount that thetripod shaft parts 22 slide, the above-described effects can bemaintained and a power can be transmitted at the same time. Further, inaccordance with the above-described structure, a structure may be usedthat can suppress a slide between rolling elements 50 and theintermediate member as the integral member. Further, when theintermediate member is integrally formed, a constant velocity joint isexcellent in its productivity or simple attachment. However, when theintermediate member 940 is formed with one pair of independent members,the generation of an induced thrust force can be reduced. Namely, inorder to decrease a width of the roller unit 930 in the direction of therotation axis of the outer ring 10, a sufficient size of the powertransmission surface is ensured without shortening a block fortransmitting a power and enlarging the outside diameter of the outerring 10.

Tenth Exemplary Embodiment

Now, a constant velocity joint 1001 of a tenth exemplary embodiment willbe described by referring to FIG. 41 to FIG. 42. The same parts as thoseof the second exemplary embodiment are designated by the same referencenumerals and an explanation thereof will be omitted. FIG. 41 is a viewof a constant velocity joint 1001 excluding an outer ring seen from thedirection of a tripod axis.

As shown in FIG. 41 and FIG. 42, the constant velocity joint 1001includes an outer ring 110, a tripod 20 and a roller unit 1030. Here,the constant velocity joint 1001 of the tenth exemplary embodiment ismainly different in view of a point that the rolling element 150 of theconstant velocity joint 901 of the ninth exemplary embodiment is changedfrom the needle to a spherical member. In accordance therewith, theforms of side surfaces of raceway grooves 111 of the outer ring 110 andconfigurations of outer surfaces of one pair of intermediate members1040 are different from those of the constant velocity joint 901 of theninth exemplary embodiment. Since the tripod 20 is the same as thetripod 20 of the first exemplary embodiment, a detailed explanationthereof will be omitted. Only different points will be described below.

The intermediate member 1040 includes one pair of intermediate members1040 a and 1040 b. As shown in FIG. 41, power transmission surfaces 1042of the one pair of intermediate members 1040 a and 1040 b have recessedgrooves formed so as to define spherical surfaces of rolling elements150 as spherical members. Other structures of the power transmissionsurface 1042 are the same as those of the ninth exemplary embodiment.Further, in order to ensure a sufficient power transmission by therolling elements 150 as the spherical members, a vertical width W3 ofthe power transmission surface 1042 in FIG. 42 is larger than that ofthe ninth exemplary embodiment.

A cage 1060 has an annular shape as an entire form similarly to the casethat the rolling element is the needle. While the circulating pathforming members 1061 and 1062 that form the cage 1060 of the firstexemplary embodiment are respectively configured in U shaped forms,circulating path forming members 1061 and 1062 of the cage 1060 of thetenth exemplary embodiment are arranged so as to be opposed in thevertical direction in FIG. 41 and provided with circular arc recessedgrooves so as to support the spherical rolling elements 150. Further, inaccordance with the enlargement of the width W3, a width W4 of the cage1060 in the axial direction of the outer ring is also larger than thatof the ninth exemplary embodiment.

In the cage 1060 of the tenth exemplary embodiment, bent parts 1061 cand 1062 c of an opening side of the outer ring and bent parts 1061 dand 1062 d of an interior side of the outer ring which do not contributeto a power transmission are not provided with opening parts in order tomore assuredly hold and circulate the rolling elements 150. Accordingly,in the tenth exemplary embodiment, a vertical width W6 in the axialdirection of the outer ring in the roller unit 1030 in FIG. 42 is equalto W4.

Now, an operation of the above-described constant velocity joint 1001will be described by referring to FIG. 43. FIG. 43 is a side viewshowing a state that a joint angle is taken and the outer ring 110 isremoved for the purpose of a simple explanation in the attached constantvelocity joint 1001. In FIG. 43, a left side shows the opening side ofthe outer ring 110 and a right side shows the interior side of the outerring 110.

In the constant velocity joint 1001, differently from the case that therolling element 150 is the needle, the spherical surfaces of the rollingelements 150 abut on the circular arc recessed grooves of theintermediate members 1040 a and 1040 b respectively and the rollingelements 150 are circulated on outer peripheries of the intermediatemembers 1040 a and 1040 b to transmit a power.

Further, as described in the ninth exemplary embodiment, during a powertransmission, the roller unit 1030 is reciprocated in the extendingdirection of the raceway grooves 111. In the reciprocating movement ofthe roller unit 1030, when the roller unit 1030 is located at a positionof a most interior side of the outer ring 110 as shown in FIG. 43, anintermediate shaft comes closest to the cage 1060 of the roller unit1030. Here, when the cage 1060 interferes with the intermediate shaft ata prescribed joint angle, an angle immediately before the interferencearises is a maximum joint angle which can be taken by the outer ring 110and the intermediate shaft.

Here, the center X1 of a part of the one pair of intermediate members1040 corresponding to a circular hole is shifted by W1 to the openingside of the outer ring 110 from the central part X2 in the width W6 ofthe roller unit 1030 in the axial direction of the outer ring, the widthW4 of the cage 1060 in the axial direction of the outer ring, the widthW2 of the intermediate members 1040 a and 1040 b in the axial directionof the outer ring and the width W3 of the power transmission surface1042 in the axial direction of the outer ring. Accordingly, the rollerunit 1030 is located to be entirely shifted by W1 to the interior sideof the outer ring 110 from the central axis Xl of the tripod shaft parts22.

Thus, as shown in FIG. 43, since the cage 1060 located in the outermostside of the roller unit 1030 moves to the interior side of the outerring 110, the intermediate shaft can take the more an angle. Namely, asufficient size of the power transmission surface is ensured withoutshortening a block for transmitting a power and enlarging the outsidediameter of the outer ring 110 to decrease a width of the roller unit1030 in the direction of the rotation axis of the outer ring 110.

Further, the rolling element 150 as the spherical member is high in itsrigidity and excellent in its circulating property. Further, thespherical member having the small number of working processes isrelatively easily produced and an attachment of the constant velocityjoint 1001 can be simplified.

Eleventh Exemplary Embodiment

Nov, a constant velocity joint 1101 of an eleventh exemplary embodimentwill be described below by referring to FIG. 44. FIG. 44 is a radiallysectional view of a part of the constant velocity joint 1101 of theeleventh exemplary embodiment. As shown in FIG. 44, the constantvelocity joint 1101 includes an outer ring 110, a tripod 20 and a rollerunit 1130. Here, the constant velocity joint 1101 of the eleventhexemplary embodiment is different in view of a point that the rollingelement 150 of the constant velocity joint 1001 of the tenth exemplaryembodiment is changed from the spherical member to a barrel shapedroller. Only different points will be described below.

Namely, the roller unit 1130 includes an intermediate member 1140, aplurality of rolling elements 1150 and a cage 1160. The rolling element1150 is the barrel shaped roller and a plurality of rolling elements arearranged so as to circulate on an outer periphery of the intermediatemember 1140 as in the case of the spherical member and the needle. Thebarrel shaped roller is the rolling element that has a pillar shape andin which a section cut in the direction orthogonal to the extendingdirection of the pillar is circular and a part corresponding to an outerperipheral surface in the section cut in the extending direction of thepillar has a circular arc protruding shape.

In accordance with such a structure, similarly to the rolling member 150in the tenth exemplary embodiment, a maximum joint angle can beincreased and a width of the pillar in the direction orthogonal to theextending direction of the pillar can be decreased more than that of thespherical member. As a result, an entire part of the constant velocityjoint 1101 can be made to be compact.

It is to be understood that the present invention can be variouslychanged within a range where the gist of the present invention is notchanged. The present invention is described in detail by referring tospecific exemplary embodiments, however, it is to be understood to aperson with ordinary skill in the art that various changes ormodifications can be made without departing the spirit, the scope or thescope of intention of the present invention.

The present invention is based on three Japanese patent applications(Application No. 2008-164967, Application No. 2008-164978, ApplicationNo. 2008-165016) filed on Jun. 24, 2008 and the contents thereof areincorporated herein as references.

INDUSTRIAL APPLICABILITY

According to the present invention, the generation of an induced thrustforce caused by a slide of a member from raceway grooves that abuts onthe raceway grooves of an outer ring. Further, according to the presentinvention, a maximum joint angle can be increased without enlarging theoutside diameter of the outer ring.

DESCRIPTION OF REFERENCE SYMBOLS

1, 101, 201, 301, 401, 501, 601, 701, 801, 901, 1001, 1101: constantvelocity joint

10, 110: outer ring

11, 111: raceway groove

12: engaging protrusion

13: rotation axis of outer ring

20: tripod

21: boss part

21 a: inner peripheral spline

22: tripod shaft part

23: rotation axis of intermediate shaft

30, 130: roller unit

40, 140, 540, 940, 1040, 1140: intermediate member

40 a, 40 b, 140 a, 140 b, 540 a, 540 b, 940 a, 940 b, 1040 a, 1040 b,1140 a, 1140 b: each intermediate member

41, 941: tripod contact surface

42, 142, 942: power transmission surface

43, 143: intermediate member introducing surface

44, 45, 944, 945: axial end face

50, 150, 250, 1150: rolling element

51: cylindrical part

52: small diameter shaft part

60, 160, 560, 660, 760, 860, 960, 1060, 1160: cage

61, 62, 161, 162, 561, 562, 661, 662, 761, 762, 861, 862, 961, 962,1061, 1062: circulating path forming member

61 a, 61 b, 961 a, 961 b, 1061 a, 1061 b: straight line part

61 c, 61 d, 961 c, 961 d, 1061 c, 1061 d: bent part

561 a, 562 a, 761 a. 762 a, 861 a, 862 a: first circulating path

561 b, 562 a, 761 b, 762 a, 861 b, 862 b: second circulating path

561 c, 562 a, 761 c, 762 a, 861 c, 862 c: third circulating path

561 d, 562 a, 661 d, 662 a, 761 d, 762 d, 861 d, 862 d: fourthcirculating path

63, 64: connecting part

302: outer ring PCR

303: tripod PCR

304: intersection

305: center of curvature

306: reference load point

307: first load point

308: second load point

1. A sliding type tripod constant velocity joint comprising: an outerring of a tubular form having three raceway grooves which are formed onan inner peripheral surface and which extend in a direction of arotation axis of the outer ring; a tripod including a boss partconnected to a shaft and three tripod shaft parts which are providedupright so as to extend outward in a radial direction of the boss partfrom an outer peripheral surface of the boss part and which are insertedinto the raceway grooves, respectively; an intermediate member which isprovided on an outer periphery of a corresponding one of the tripodshaft parts so as to be oscillated relative to the corresponding one ofthe tripod shaft parts and which has power transmission surfaces on bothside surfaces and opposing the side surfaces of a corresponding one ofthe raceway grooves; a plurality of rolling elements provided betweenthe side surfaces of the corresponding one of the raceway grooves andthe power transmission surfaces so as to roll along the side surfaces ofthe corresponding one of the raceway grooves; and a cage that supportsthe rolling elements such that the rolling elements circulate on anouter periphery of the intermediate member, wherein the cage includes: afirst circulating path which is located between one of the powertransmission surfaces and one of the side surfaces of the correspondingone of the raceway grooves and which supports the rolling elements; asecond circulating path which is located between the other of the powertransmission surfaces and the other of the side surfaces of thecorresponding one of the raceway grooves and which supports the rollingelements; a third circulating path which connects one ends of the firstand second circulating paths located in an opening side of the outerring and which is foamed to be bent in at least in one direction of aradially outward direction of the outer ring and a direction toward thetripod shaft parts so as to have a protruding shape; and a fourthcirculating path which connects the other ends of the first and secondcirculating paths which are located in the interior side of the outerring.
 2. The sliding type tripod constant velocity joint according toclaim 1, wherein a central part in a circumferential direction of theouter ring in the third circulating path is most bent in at least in onedirection of the radially outward direction of the outer ring and thedirection toward the tripod shaft parts so as to have the protrudingshape.
 3. The sliding type tripod constant velocity joint according toclaim 2, wherein the first, second, third and fourth circulating pathshave opening parts over an entire length in an outer peripheral side ofthe cage, and wherein widths of the opening parts of the third andfourth circulating paths are narrower than widths of the opening partsof the first and second circulating paths.
 4. The sliding type tripodconstant velocity joint according to claim 1, wherein the third andfourth circulating paths are formed to be symmetrical with respect tothe corresponding one of the tripod shaft parts.